A motor operated power steering device which transmits rotational force from a steering assistance motor to a steering shaft by way of a gear fitted around the outer circumference of the steering shaft. A torque limiter fitted in between the steering shaft and the gear comprises a torque setting member, which is subject to diametric deformation as a result of being fitted in between the outer circumference of the steering shaft and the inner circumference of the gear. Diametric force is applied to the steering shaft and the gear in accordance with the diametric deformation of the torque setting member. The limit torque value of the torque limiter corresponds to the diametric deformation of the torque setting member.