A coin discriminating device has a detecting part, a first switching part, a storage part, and a control part. The detecting part has a first sensor including a pair of coils, and an oscillating circuit, and is supplied with voltage from a power source, and in addition, outputs a detection signal varied by a coin passing between the coils. The first switching part switches magnetic connection of the coils between an in-phase connection and a reversed-phase connection a plurality of times while the coin passes between the coils. The control part compares the detection signal from the detecting part and a reference signal stored in the storage part so as to determine authentication and a denomination of the coin.