A magnetic sensor includes a magneto-electric transducer, a switch circuit, an amplifier circuit, a subtractor circuit, and a selector circuit. The subtractor circuit performs a first subtraction process of generating a first subtraction voltage by subtracting an amplification voltage obtained under an immediately prior first bias state from an amplification voltage obtained under a second bias state and a second subtraction process of generating a second subtraction voltage by subtracting an amplification voltage obtained under an immediately prior second bias state from an amplification voltage obtained under a first bias state in a serial and parallel manner. The selector circuit alternately selects the first subtraction voltage and the second subtraction voltage to output a select voltage.