An emergency stop switch and an emergency stop switch circuit which are used for stopping a machine in case of emergency. The emergency stop switch (10) has a transformer-like structure provided with a first core member (14) wound with first and second windings and a second core member (15) which is usually brought into contact with the first member (14) by means of a spring and is separated from the first member (14) when a push-button (16) is pressed. The emergency stop switch circuit is constituted by connecting a plurality of emergency stop switches (10) in series.