Abstract: A driving device includes an electric motor, a drive gear, a deceleration mechanism, a driven gear, and a housing. At least either one of the drive gear and the driven gear is provided as a helical gear. The deceleration mechanism includes a plurality of reduction gear shafts, a plurality of bearings, and a biasing member provided for at least any one of the bearings. The biasing member axially biases an outer ring of the at least any one of the bearings that supports at least either one of end parts of the shaft portion of a corresponding one of the reduction gear shafts, the end parts including an end part on the large-diameter gear wheel side and an end part on the small-diameter gear wheel side.