A driving device and a seat adjusting mechanism for vehicle are provided. The driving device includes a motor and a gearbox. The gearbox includes a worm and a worm gear. The worm is fixedly connected to an output shaft of the motor. The gearbox further includes first and second driving gears, and first and second driven gears. The first and second driving gears are coaxially fixed to the worm gear and located at two sides of the worm gear, respectively. The first and second driven gears are fixed coaxially with each other and engaged with the first and second driving gears, respectively. Two driving gears are arranged at the two sides of the worm gear symmetrically, and two driven gears are also arranged at the two sides of the worm gear symmetrically, which results in a compact structure and reduced volume of the driving device.