A drive device includes a reduction gear, a receiving portion and an output unit. The reduction gear unit has at least two helical gears of resin, which mesh with each other. The at least two helical gears include a helical gear output side and another helical gear. The expenditure-helical gear is disposed closer to a power transmitting path of the reduction gear to the output unit than the other helical gear. The housing cover includes a restricting portion which is disposed in a range including a straight line which intersects the first center axis and the second center axis. The restricting portion faces a bottom of the gear receiving portion. The limitation section is designed such that it allows a sliding contact with the discharge-side helical gear to limit an axial deflection of the output side helical gear.