A control unit including a plurality of boards is formed of a single multilayer metal substrate, whereby an electric power steering apparatus can be obtained in which connection members for connecting between the boards are made unnecessary, so the size and cost of the apparatus can be reduced, and the reliability of bonding can be improved. In the electric power steering apparatus, a power main body (20a) and a control main body (20b) are mounted on a metal substrate (22), and the power main body (20a) and the control main body (20b) are electrically connected to each other by wiring patterns (26a through 26e) and metal columns 28a through 28d in the metal substrate 22.