To stably discriminate the outer diameter of a coin, and to improve discriminating accuracy.

An outer diameter detection sensor 25a-1 between outer diameter detection sensors 25a-1 and 25a-2 which detect the outer diameter of a coin C to be conveyed according to the rotation of a conveyance disk 16 in a state that the coin C is received by a coin reception part 17 is arranged in an outer peripheral side area on a conveyance locus of a coin C, and the outer diameter detection sensor 25a-2 is arranged in an inner peripheral side area on the conveyance locus of the coin C, and when the coin passes, the outputs of the two outer diameter detection sensors 25a-1 and 25a-2 are added so that the outer diameter of the coin can be measured. Thus, it is possible to reduce the variance of measurement values even when a coin having a small diameter rattles in the coin reception part 17 during the conveyance of the coin.