To fix a code wheel in the axial direction of shaft without providing a cut becoming a dead space in a substrate.

In the photosensor module, a light receiving element module containing a light receiving element and a light emitting element module containing a light emitting element are constituted of a pair of separate components, and a substrate unit where one light receiving element module or light emitting element module is fixed to a printed board is secured to the end face of a motor. After a code wheel is fixed to a motor shaft in the axial direction thereof and secured, a substantially L-shaped module holder containing the other light emitting element module or light receiving element module is fixed to the substrate unit. The light emitting element and the light receiving element are positioned to oppose each other through the optical modulation track portion of the code wheel.

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