In an electromagnetic flow meter, a signal amplifying circuit has an FET-input type differential amplifier wherein one input terminal is connected to a flow rate signal input terminal and the other input terminal is connected to a flow rate signal input terminal. An amplified output signal, which is obtained through performing differential amplification on the flow rate signals, is outputted from an output terminal. A fault detecting circuit detects a fault in the flow rate signal through comparing the electropotential of the amplified output signal to an upper limit reference electropotential and a lower limit reference electropotential.