To provide a magnetizing apparatus for magnetic flaw detection capable of immediately demagnetizing remanence of a test object after a magnetic flaw detection.

When a changeover switch 4 is turned on, an amplifier circuit 23 generates a magnetization AC from a DC output from a battery 21 and boosted by a booster circuit 22, and a magnetization sinusoidal AC output from a sine wave generating circuit 24, and outputs it to a magnetization coil 12. When the changeover switch 4 is turned from the on state to an off state, the sine wave generating circuit 24 outputs a demagnetization sinusoidal AC attenuating with time, to the amplifier circuit 23. The amplifier circuit 23 generates a demagnetization AC on the basis of the DC boosted by the booster circuit 22 and the demagnetization sinusoidal AC to output it to the magnetization coil 12.