Optical encoder device for small-sized motor

A photo sensor module includes a holder made of resin and a light-emitting element and a light-receiving element accommodated in the holder. A printed circuit board is fixed to a flat side wall portion of a motor. The resin holder has a guide portion which is formed integrally therewith and which comes into contact with an end surface and a bearing-holding portion of an end bell. The printed circuit board is fixed in a state in which the guide portion is sandwiched between the bearing-holding portion and the printed circuit board while being brought into contact with the end surface of the end bell, whereby the photo sensor module is positioned in thrust and radial directions of the motor.