To stop a steering assist naturally without giving an uncomfortable feeling to a driver even when the steering assist is stopped abnormally in a low power supply voltage environment in operation and control of an electric power steering device.

Even when a stop of the steering assist occurs due to a failure of a motor driving circuit when a power supply voltage is decreased, a space between motor terminals is short-circuited by a relay, and an electromagnetic brake by a motor is generated, thereby easing kickback when the assist is stopped.