At a Racing Victoria hearing in Melbourne, Oliver admitted to placing the bet on favourite Miss Octopussy in a race at Moonee Valley in October 2010.
Miss Octopussy won the race while Oliver's mount Europa Point, the second favourite, finished sixth.
"I apologised for a spur of the moment decision that I will regret for the rest of my of career and beyond," the 40-year-old said after the hearing.
"There were a lot of difficult personal issues going in my life at the time, however there are no excuses for the fact that I breached the trust of many people in the industry and I broke a fundamental rule of racing."
One of his country's most successful jockeys, Oliver has twice won the Melbourne Cup and completed the grand slam of Australia racing with wins in the Caulfield Cup, Cox Plate and Golden Slipper.
Oliver's 2002 Melbourne Cup triumph on Media Puzzle came only days after his brother was killed after falling from his mount at Perth's Belmont racecourse.
Jockeys are forbidden from betting on any horse races in Australia, let alone on races in which they ride.