A magnetic sensor circuit has Hall devices 10X and 10Y, selection switch circuits 20X and 20Y, amplifier units 30X ad 30Y, a comparison unit 60, capacitors 41X, 42X, 41Y, and 42Y, and switch circuits 51 and 52. The Hall voltages obtained from the Hall devices 10X and 10Y are outputted in either of a first and a second states switched by the selection switch circuits 20X and 20Y. The amplifier units 30X ad 30Y each operate differentially and, if the difference between their outputs is greater than a set hysteresis width, the output logic of a detection signal Sdet is shifted. This configuration helps reduce the influence of device offset voltages in the Hall devices, and also helps reduce the influence of input offset voltages arising in the amplifiers.