To provide a game machine which enables the free arraying of even a relatively narrow space within a playing area while allowing the efficient sensing of the passage of game balls.

In the pachinko game machine, a game ball passage sensor P which has the first sensor part 111a comprising a light projecting element and a photodetector and the second sensor part 111b comprising a light shielding member 31 as a detection body in the detection with the first sensor part 111a is provided in a ball introduction guide path of the second route which guides the game balls to win a starter chucker at a high probability. The light shielding member 31 is set to freely stick out into the guide path and made to move forward or backward between the light projecting element and the photodetector of the first sensor part 111a to output an ON/OFF signal.