An induction heater comprising: an inverter including an induction heating coil which produces a high-frequency magnetic field capable of induction-heating an object made of aluminum, a control section for controlling the output of said inverter, and a movement detection section (3116, 3117) which detects a state of operation of said inverter or a state of said object until the output of said induction heating coil increases gradually from a low output to a predetermined output to detect a movement of said object, the movement of said object including floating of said object by the high-frequency magnetic field produced by the induction heating coil; characterized in that, when said movement detection section performs the movement detection operation for detecting the movement of said object, said control section performs the output limiting operation for limiting the output of said induction heating coil to a value lower than the value when the movement thereof has been detected or stopping the heating, afterwards, repeats at least once the process of canceling said output limiting operation, increasing the output gradually again, performing said movement detection operation, and performing said output limiting operation, and when detecting that said movement detection operation is repeated with approximately the same output changes, said control section determines that the floating of said object has been caused by the high-frequency magnetic field produced by said induction heating coil, thereby limiting the output of said induction heating coil thereafter to the output lower than the output when detecting the floating of said object to carry out heating. an inverter including an induction heating coil which produces a high-frequency magnetic field capable of induction-heating an object made of aluminum, a control section for controlling the output of said inverter, and a movement detection section (3116, 3117) which detects a state of operation of said inverter or a state of said object until the output of said induction heating coil increases gradually from a low output to a predetermined output to detect a movement of said object, the movement of said object including floating of said object by the high-frequency magnetic field produced by the induction heating coil; characterized in that, when said movement detection section performs the movement detection operation for detecting the movement of said object, said control section performs the output limiting operation for limiting the output of said induction heating coil to a value lower than the value when the movement thereof has been detected or stopping the heating, afterwards, repeats at least once the process of canceling said output limiting operation, increasing the output gradually again, performing said movement detection operation, and performing said output limiting operation, and when detecting that said movement detection operation is repeated with approximately the same output changes, said control section determines that the floating of said object has been caused by the high-frequency magnetic field produced by said induction heating coil, thereby limiting the output of said induction heating coil thereafter to the output lower than the output when detecting the floating of said object to carry out heating.