An inverter circuit converts electric power supplied to a motor by on/off operations of FETs. A microcomputer controls driving of the motor by controlling the on/off operations of the FETs. The microcomputer operates as a current direction determination part. The microcomputer detects a first potential difference, which is a potential difference between both ends of each diode, and a second potential difference, which is a potential difference between both ends of each diode, when both FETs of each phase are in an off-state. The microcomputer can further determine a direction of current flowing in the motor based on the detected first potential difference and the detected second potential difference.