PURPOSE: To make a wheel inexpensive and lightweight, to eliminate the clogging of foreign matter, and to prevent a detection error from being generated by providing a metal plate which has many cuts formed at its outer periphery by press punching, and inserting the metal plate into one side of a wheel made of synthetic resin and uniting them.

CONSTITUTION: The metal plate 1 is punched by pressing in a disk shape to have many cuts 2 at its outer peripheral part. The wheel 3 is molded out of the synthetic resin in a disk shape and the metal plate 1 is inserted into one side in one body. Then the wheel 3 is clamped to the flank of the wheel 4 with the metal plate 1 out by using bolts and an electromagnetic pickup 5 is arranged nearby the cuts 2 of the metal plate 1. The pickup 5 detects pulses by the rotation of the cuts 2 of the wheel 3 rotating together with the wheel 4 to detect the rotating speed. The resin is supplied to between the cuts 2 of the metal plate 1 at the time of the molding and the wheel 3 is made lightweight without chipping any cut 2 nor clogging any cut with foreign matter.