Provided is a motor unit capable of preventing breakage/deformation of a worm, even when a load application means being a worm gear mechanism that applies a load to gear train rotation is attached to a case manually. Specifically, a load when a worker grasps the load application means using their fingers is supported by an upper frame and worm breakage/deformation is prevented, as a result coupling a first bearing and a second bearing at a position above the support position for the worm, by using the upper frame being the upper end section of a frame, in the load application means which has the worm, the first bearing and the second bearing that rotatably support the worm, the frame that couples the first bearing and the second bearing, and a brake that applies resistance to the rotation of the worm.