Abstract: An arrangement of circuit casings and circuit boards in a motorized power steering device including a drive circuit casing, a control circuit casing and a gear casing connected to the drive circuit casing. The drive circuit casing includes a drive circuit board provided thereon with a drive circuit whereas the control circuit casing includes a control circuit board provided thereon with a control circuit for outputting a control signal to the drive circuit. An electric motor is attached to the drive circuit casing such that the drive circuit casing is interposed between the gear casing and the electric motor.