A magnetic sensor includes a magnetic sensitive member 11 including an amorphous wire, a detection coil 12 wound around the magnetic sensitive member 11, and a sample-and-hold circuit for detecting a voltage induced in the amorphous wire 11 when a pulse current is interrupted. The sample-and-hold circuit has a sample-and-hold unit B31 and a delay circuit. The sample-and-hold unit B31 includes an electronic switch S31, a capacitor C32, a resistor R32, a resistor R33, and a high-input amplifier A31. The delay circuit includes a resistor R31 connected to a control terminal of the electronic switch S31 and a capacitor C31.