A motor-driven compressor includes a cluster block, which accommodates a connecting terminal. The connecting terminal connects an electric motor to a motor driving circuit. A second insulator includes a tubular base, extended portions, which extend from the base, and insulator flanges. Each insulator flange is located on an opposite end of each extended portion from the base. The cluster block is fastened to some of the insulator flanges on the opposite side of the insulator flanges from the extended portions. The cluster block includes a second wall, which faces some of the insulator flanges. The second wall includes engagement pieces, which project in the radial direction of the rotary shaft. The engagement pieces are each fitted to an opening portion, which is a gap between the insulator flanges that are adjacent to each other in the circumferential direction of the rotary shaft.