An insert insertion tool includes a mandrel on which an insert is mounted, and a coating member. The coating member is configured to apply ink to a rear end of the insert on an opposite side of a tip end of the insert that first enters a tap hole. Accordingly, the insert inserted into the tap hole stands out on a surface of a workpiece, and a user is capable of visually recognizing whether or not the insert has been inserted into the tap hole. Thus, the confirmation work becomes easy, and it is possible to improve the work efficiency.