A drive apparatus for an opening/closing body for a vehicle includes a drive unit including a rotational drive apparatus, a reduction gear mechanism linked with a rotational shaft of the rotational drive apparatus, and an output member linked with the rotational shaft through the reduction gear mechanism and linked with the opening/closing body through a connection member, a first pulse signal generator provided at the drive unit and generating a first pulse signal on the basis of a rotation of the rotational shaft, a second pulse signal generator provided at the drive unit and generating a second pulse signal on the basis of a rotation of either one of the reduction gear mechanism and the output member, and a control means for calculating an opening/closing position of the opening/closing body on the basis of the first pulse signal emitted by the first pulse signal generator utilizing the second pulse signal emitted by the second pulse signal generator as a base point and controlling the rotational drive apparatus corresponding to the opening/closing position of the opening/closing body.