PURPOSE: To count the number of ball with high accuracy, by taking the length of a ball in the passing direction passing through a tube as a function of a pulse number having a prescribed width and comparing the result with other large or small foreign material.

CONSTITUTION: The ball 7 passing through the tube 9 shuts a ray irradiated from a light source 2 and a photoelectric tube 3 detects the ball or a foreign material. Further, the pulse number having a prescribed width generated from a pulse generator 35 from the start and the end of detection is counted at a pulse counter 36, the pulse is compared with the pulse number having a prescribed width at the passing of the ball having a preset upper and lower limit size, the disrimination and comparison between the ball and other large or small foreign material are attained at a foreign material discriminator 37. When discriminated as a ball, the pulse is counted at a ball counter 31. Thus, the number of ball is counted with high accuracy.