To accurately detect parts, which are arranged in a tape, by irradiating the parts arranged in the tape with the light, and photoelectrically detecting the transmitted light, which is transmitted through the part, with a transmission type photoelectric sensor, and counting the number of parts arranged in the tape on the basis of the detected electric signal.

A tape 12 is moved forward an backward by a sprocket 2, and the tape 12, in which parts 11 are arranged, is wound around a winding reel 3 from a part reel 1 wound with the tape 12, in which the parts 11 are arranged. The parts 11 arranged in the tape 12 are irradiated with the light and the transmitted light, which is transmitted through the parts 11, is photoelectrically detected by a transmission type photoelectric sensor 14, and the number of the parts 11 arranged in the tape 12 is counted by a counter 6 on the basis of the electric signal detected by the transmission type photoelectric sensor 4.