The present invention relates to an oil supply device for use in an automatic transmission mounted on a vehicle, and is applied to a vehicle in which an idle reduction control or the like is performed. The oil supply device includes an oil pump which is driven by a driving motor of a vehicle and a motor separate from the driving motor, and an engagement and disengagement element which transmits a driving force of the driving motor to the oil pump, and the oil pump is driven by the motor without using a drive system of the driving motor.