To provide an inspection method for an encoder capable of efficiently inspecting whether an inclination angle of a boundary between an S pole and an N pole existing on a face to be detected of an encoder 4 is accurate as designed.

While a detecting section of an inspection sensor 10 is made to face the face to be detected, a work for changing an output signal of the inspection sensor 10 by rotating the encoder 4 is carried out at a plurality of positions on the face to be detected in a width direction. In addition, a phase difference between each of output signals obtained at the plurality of positions in the width direction and a predetermined reference signal is obtained. It is confirmed whether an inclination in a change of each phase difference in relation to the face to be detected in the width direction is within a predetermined range. It is inspected whether the inclination angle of the boundary is accurate as designed on the basis of the above confirmation, thereby solving the problem.