An electric-power control device including a substrate of an annular shape in which a through hole is formed and a connector is arranged in a peripheral part, the electric-power control device driving an electric motor. On the substrate, a power semiconductor module is mounted on a first region on one side relative to a straight line connecting the center of the through hole to the center of the connector, and a microcomputer is mounted on a second region on the other side. Furthermore, a first ground pattern part that is formed extending from the power semiconductor module toward the connector in the first region and a second ground pattern part that is formed extending from the microcomputer toward the connector in the second region are provided on the substrate.