PURPOSE: To enable self-diagnosis on the propriety of a detecting function of the apparatus, by providing a pinhole for resting to always inspect operating condition of a detection system.

CONSTITUTION: When a pinhole 13 for testing gets to a test position, light from a light source 10 reaches a photosensor passing through the pinhole 13 for testing. So, when the photosensor operates normally, a level discrimination circuit outputs a light leakage signal '1'. On the other hand, an angle signal generation circuit outputs a test position signal at this position. Then, as these signals are supplied to a detection system deficiency signal generation circuit, the detection system deficiency signal generation circuit judges that no abnormality exists and outputs no deficiency signal. On the other hand, when there is no output from the photosensor 9 with the pinhole 13 at the test position, a light leakage signal remains '0' from a level discrimination circuit. Thus, the detection system deficiency signal generation circuit sends the deficiency signal to an interface to stop the rotation of a turret disc 1 through a main motor interlock or the like and an alarm is outputted while the flow of cans 3 can be stopped.