He had the biggest majority of any MSP - 10,530 - when he won Banff and Buchan this year and he is sitting on one of the biggest financial nest-eggs of any member at Holyrood.
As well as the 30,000 of shares he had in Iberdrola- ScottishPower, he also owns 440,000 worth of shares in Halifax Bank of Scotland (HBOS).
His wealth comes from his 30 years of service to the Bank of Scotland. He started working there in 1969 and led the IT division, becoming its director of technology and innovation.
It was as a bank executive that he made his money, leaving the company in 1999 with enough behind him to finance a change of career into politics.
Now 60, Mr Stevenson is one of the older ministers in Alex Salmond's Scottish Government and one of the few - along with the millionaire Jim Mather - to have made a substantial amount of money in the private sector before going into politics.
He is not new to controversy. Earlier this year, it emerged that he was using a parliamentary allowance to help pay for a second house, just yards from his former family home.
The minister lived in a three-storey family home in Linlithgow, West Lothian, for more than 30 years. But when he won the Banff and Buchan constituency in 2001, he decided to move his family there. He bought a new house in 2002 for 165,000, then sold the Linlithgow home for more than 280,000 in 2003.
Weeks later, he bought another house in the town for 170,000 - meaning he qualified for the allowance that helps MSPs live near the parliament.
Since then, he has claimed more than 20,000 in accommodation allowance as well as 1,000 a year towards his council tax. Mr Stevenson had not broken any rules, but he was one of a series of MSPs whose actions forced a review of the whole allowances system for MSPs.
The son of a doctor and a teacher, he was born in Edinburgh and went to school in Fife before going on to university in Aberdeen. A former psychiatric nurse, he moved into computers when they were in their infancy, joining the Bank of Scotland in 1969, which is where he stayed until 1999.
By that stage, he had become deeply involved in SNP politics and he spent the 1992 election campaign driving Mr Salmond around Scotland.
In 2001, he replaced Mr Salmond as the MSP for Banff and Buchan when the SNP leader decided to stay at Westminster rather than continue in the Scottish Parliament.
He made his maiden speech on the European Union's common fisheries policy, rising to his feet at 4:11pm on 14 June, 26 hours and 36 minutes after being sworn in as an MSP.
By the end of parliament's second session, on 2 April, 2007, he had made 284 speeches and is thus the most prolific speaker since the parliament was reconvened in 1999.
He lives in Banffshire with his wife, Sandra.
MSPs have to abide by a series of clear rules to make sure they do not become involved in any conflicts of interest:
• They have to adhere to the MSPs' code of conduct. This states that MSPs have to declare any financial interests which may be seen to prejudice their work at Holyrood.
There is a "prejudice" test and the code states: "An interest meets the test if, taking into account all the circumstances, the interest would reasonably be considered to prejudice, or reasonably be considered to appear to prejudice, the ability of the member to participate in a disinterested manner in any parliamentary proceedings."
• Ministers also have to abide by the ministerial code of conduct. One part of this, section nine, deals with potential conflicts of interest.
Part 9.1 states: "Ministers will want to order their affairs so that no conflict arises or is thought to arise between their private interests [financial or otherwise] and their public duties.
"It is the personal responsibility of each minister to decide whether and what action is needed to avoid a conflict or the perception of conflict, and to defend that decision, if necessary by accounting for it in the parliament. Where there is a doubt it will almost always be better to relinquish or dispose of the interest.
And point 9.5 adds: "If an allegation is made that a particular minister has a conflict of interest, it must be for that minister to explain their position and justify what has been done."
• The ministerial code of conduct makes it clear that ministers should seek a meeting with the permanent secretary of the Scottish Government if they have any doubts about their financial interests.
• It also suggests ways of dealing with financial interests if there is a perception of a conflict of interest. According to paragraph 9.13 of the code, ministers can put their shareholdings in "bare" or blind trusts, but these only really work for portfolios of different shares, not single-company shares. Alternatively, they could accept an obligation not to trade in the shares while they are ministers.