The present invention is intended to provide a protective cover having a reliable sensor holder part that prevents reduction in air tightness and strength of a division wall between a magnetic sensor and a magnetic encoder.

A protective cover 1 is press-fitted into an outer ring to seal one axial end portion of a bearing, and has a sensor holder part 3B holding a magnetic sensor A. In the protective cover 1, a disc-shaped member 3 has a thick part 6 as a flow path for preferentially charging a molten resin into a thin part for forming a division wall B in a cavity of a molding die for use in injection molding between a position corresponding to a gate of the molding die and the division wall B.

An optical element made of resin includes a first surface configured to serve as an optical surface, a second surface configured to serve as an optical surface, a third surface configured to serve as an optical surface, and a fourth surface configured to connect to the third surface. The third surface includes a peripheral area and an inner area, and a distance from an outer edge of the third surface to a position in the peripheral area is equal to or smaller than 5 mm and a distance from the outer edge of the third surface to a position in the inner area is larger than 5 mm. A weld is formed in at least any one of the peripheral area of the third surface and the fourth surface.