To provide an electric power steering device capable of suppressing the gear rattling noise or the like by realizing the adequate engagement of a worm without increasing the number of components or causing any defective engagement by misalignment.

The turning angle 1 in an example in Fig. 1(a) becomes a relatively large value, and a large clearance must be formed between an inner ring of a bearing for support at a point A and a rotary shaft. Thus, troubles such as vibrations, abnormal noise and fretting may occur. According to an example shown in Fig. 1(b), the stress exerted in the rotary shaft S can be reduced, troubles such as wrenching can be suppressed, and the moment load on the bearing can be reduced.