George Russell Weller, 89, was not in court to hear the verdict. He faces as much as 18 years in prison.
Weller, who is frail and in poor health, attended only the trial's opening statements.
Jurors deliberated eight days before reaching the harshest verdict possible.
Weller's attorneys argued he was a victim of "pedal error," that mistook his car's accelerator for the brake and panicked when the vehicle raced into the open-air market on July 16, 2003.
Prosecutors said he was careless to the point of criminal negligence and lacked remorse.
"He looked at what he had done, essentially shrugged his shoulders and said 'oops,"' prosecutor Ann Ambrose told the jury.
The crash left behind a devastating scene and ignited a national debate over elderly drivers.
Weller's 1992 Buick Le Sabre traveled about 300 yards, reaching speeds of 60 mph or more as it crashed into food stalls. It finally came to a stop after hitting a ditch, with one victim's body tangled underneath and another's draped across the hood.
During the trial, jurors were shown photos of victims, who ranged in age from 7 months to 78 years.
Weller did not testify, but jurors heard his taped interview with police immediately after the crash in which he said he tried everything he could think of to stop the car.
"I tried to take the control knob and jam it into park. Everything. Anything that I thought would stop the action of the car," he said.
Weller said he had no idea how many people he hit.
"But I'm deeply sorry for any pain that everyone went through," he said. "It was my fault."