Since a rigid supporting structure for a gear box GB and a rolling type
rack supporting device RSD are employed, an electric power steering
apparatus having no response delay and having a high transmission
efficiency can be realized. Further, a high steering performance required
for a long period and a steering assist force that is increasing recently
can be efficiently transmitted to wheels. Further, when the wheels
collide with a shoulder of a road to receive a counter input, a torque
sensor TS detects a torque and an assist steering force against the
counter input is outputted to an output shaft OS. Consequently, the
torque of the counter input is restrained from being transmitted to a
steering shaft SS side. Thus, a kick back and a vibration are
advantageously hardly transmitted to a steering wheel SW from the wheels.