A magnetic sensor includes: a magneto-sensing body 11 formed by an amorphous wire conducting a pulse current; a detection coil 12 wound around the magneto-sensing body 11; and a sample hold circuit for detecting voltage induced in the detection coil 12 when the pulse current is cut off. The sample hold circuit has: a sample hold section B31 consisting of an electronic switch S31, a capacitor C32,aresistor R32, a resistor R33, and a high-input resistance amplifier A31; and a delay circuit having a resistor R31 and a capacitor C31 connected to the control terminal of the electronic switch S31.