PURPOSE:To dispense with the securing of space for installing a drive circuit at the side of a body frame as well as to reduce the number of wiring for a wheel motor by constituting this drive circuit driving an electric motor integrally together with this motor, and installing it in the inner space of a wheel. CONSTITUTION:In this wheel motor 1, an electric motor 4 and a gear reducer 5 are installed in the inner space of a wheel 3. In this constitution, the wheel 3 is rotated and driven by rotational output of this motor 4. In this case, the motor 4 consists of a stator 7 clamped to a case 6 of the motor 4 being clamped to the body side, a rotator 8 installed free of rotation at an inner part of the stator 7 and an output shaft 9 transmitting rotation output if the rotator 8 to the wheel 3 via the gear reducer 5. On the other hand, a drive circuit 22 driving the motor 4 is integrally constituted together with the motor 4, installing it in an inner space of the wheel 3. In brief, the drive circuit 22 is installed in an interspace S at a portion where four gears 5a to 5d in an interval between the case 6 and the wheel 3 are not yet installed.