To perform rapid and automatic heating and cooling treatment of a tool holder, to reduce the size of a device, and to be decreased in a price.

This shrinkage fitting device is operated such that a coil is charged with an AC current, a tool holder 2 is heated by an induction current, and the shank part of a cutter 3 is securely shrinkage-fitted in its hole part. In this case, the coil consists of a pair coils 1a and 1b, a pair of the coils 1a and 1b are situated at the side of the tool holder 2. The shank part of the cutter 3 is heated in a way the coil is charged with a current such that a magnetic flux generated by the two coils 1a and 1b is always generated in the same direction. The temperature of the part, heated by the coil, of the tool holder 2 is detected by a temperature detecting means 14. When the detecting temperature reaches a temperature higher than a given temperature, heating of the coil is automatically stopped, and the tool holder is cooled by supply of air. When temperature detected by the temperature detecting means is decreased to a value lower than a given temperature, air supply through an air supply nozzle is automatically stopped.