Sir Bob, 55, who has represented the constituency since 1997, is said to be in the early stages of the disease and receiving treatment at Aberdeen Royal Infirmary.
And he has vowed to fight to retain the seat for the Lib Dems at the 2015 General Election, despite his illness
He is the chairman of Westminster’s Energy and Climate Change Select Committee and is also a Vice-Chair of the All-Party Group for the UK Offshore Oil and Gas Industry.
Sir Bob said today: “I would like to thank the medical staff at ARI for the help I am receiving. My colleagues at Westminster and locally are being very supportive, as is my family.
“This was not easy news to receive but it is a condition that can be managed and I plan to make the best I can of it.”
A spokeswoman for the MP said: “Sir Robert Smith has been diagnosed with the early stages of Parkinson’s disease. Sir Robert is receiving appropriate treatment for the disease.”
Parkinson’s disease affects one in 500 people in the UK. It can cause a tremor, muscle rigidity and slowness of movement. It is incurable but treatable with a number of drugs.
Sir Robert was recently re-selected to contest the West Aberdeenshire and Kincardine seat for the Lib Dems at the next election.
The constituency’s 2015 campaign committee chairman, Mike Rumbles, said: “I am saddened to hear that Sir Robert has this progressive illness but am delighted that he intends to keep working as our local MP and is committed to re-standing in 2015.”
Sir Bob, a graduate of Aberdeen University, worked as the manager on his family’s estate in Aberdeenshire and was an Aberdeenshire councillor between 1995 and 1997, serving as Vice-Convener of the Grampian Joint Police Board, before becoming an MP.
Married with three daughters, he served as Shadow Deputy Leader of the House of Commons between 2007 and 2010 and was Deputy Chief Whip for the Liberals between 2001 and 2006.
He retained his seat at Westminster in the 2010 General Electron with a 38.2 per cent share of the vote, taking 17,362 votes - 3,684 votes ahead of the Conservative candidate in second place.