A tool changer is composed of a support shaft, a forward/backward movement drive motor moving the support shaft upward and downward, a rotation drive motor rotating the support shaft about an axis, a tool change arm having tool grippers formed at both ends thereof, and an air blow mechanism discharging compressed air to a tool and a next tool gripped by the tool grippers. In tool change using this tool changer, in a positioning operation, the tool change arm is rotated by degrees and compressed air is discharged toward the tool and the next tool by the air blow mechanism.