A coin discriminating apparatus includes a light source for emitting light toward one surface of a coin being transported, a reflected light sensor for receiving light emitted from the light source and reflected by the coin, light emitting elements disposed downstream of the light source for emitting light toward the one surface of the coin being transported, a sensor for photoelectrically receiving light emitted from the light emitting elements and reflected by the one surface of the coin and producing image pattern data of the one surface of the coin, a memory for storing reference data of coins of each denomination, a first denomination discriminator for calculating coin diameter based on the image pattern data of the one surface of the coin produced by the sensor, comparing it with reference diameter data of coins of each denomination stored in the memory and tentatively determining the denomination of the coin, a second denomination discriminator for reading reference pattern data of coins of the denomination determined by the first denomination discriminator from the memory, comparing the reference pattern data with the image pattern data of the one surface of the coin and finally determining the denomination of the coin, and a received light amount controller for controlling an amount of light reflected by the one surface of the coin to be detected by the sensor in accordance with an amount of light reflected by the coin and detected by the reflected light sensor. According to the thus constituted coin discriminating apparatus, it is possible to discriminate whether or not coins are acceptable and the denominations of coins with high accuracy by optically detecting the surface patterns of coins.