Having bounced back from that shaky start to open with a five-under-par 66 at the Edinburgh venue before adding a 73, Bell closed with a 72 for a two-under 211 total.
He finished three shots ahead of Englishman Trevor Foster, with three other challengers from south of the Border, Alan Mew, Andrew Stracey and George Wilson, filling the next three positions on the final leaderboard.
“My putting was definitely the key this week and the Royal Burgess greens, which were in fantastic condition, really suited my eye,” said Bell, last year’s Scottish Seniors Order of Merit winner and also a member of the successful Scotland side in the European Senior Team Championship in Slovenia.
“I obviously didn’t get off to a great start on the first day, but I knuckled down and started holing a few putts after that and was able to get more aggressive.”
Bell, whose son, Ross, was in Scotland’s title-winning team in the 2012 Home Internationals, added: “I knew I had the game to win this week and the course has some similarities to Downfield, so I felt quite at home. I played a couple of practice rounds with John Fraser who is a member here, which really helped me work my way round the course.
“It was good to play with defending champion Stephen East, who is an excellent player and that also helped me focus. I’m delighted to get my first national win under my belt and look forward to challenging at Sunningdale in the British.”
Fraser, a former captain at the host club, claimed the prize for the leading over-65 in the field, finishing in joint-21st on 223 after rounds of 74-70-79.
Elsewhere, the final of the Amateur Championship at Royal St George’s will be an Ashes affair between England’s Harry Ellis and Australian Dylan Perry. Ellis came from behind to defeat Italy’s Luca Cianchetti 3&2 in his semi-final, while Perry beat Argentina’s Alejandro Tosti by the same score in the other last-four clash in Kent.
In the paid ranks, Gary Orr finished joint-tenth behind Spaniard Santiago Luna on his over-50s debut in the European Tour Properties Senior Classic in Finland, while Englishman Chris Lloyd completed back-to-back wins on the PGA EuroPro Tour with victory in the PDC Championship at Studley Wood.