To enable developing of a motion of bending forearms gradually with elbows as fulcrum in a basic action of swing, especially in back swing and follow through.

A grasping member 30 is mounted on a waist band part WB of slacks or the like and holding members 10 are mounted on right and left upper arms respectively. In the back swing, the holding members 10 mounted on the right and left arms move to separate from the grasping member 30 and an elastic member 20 extends exceeding a specified length, while the elasticity thereof acts to block the movement of the holding members 30. As a result, the movement of an upper arm is blocked naturally on the spot and the free forearms alone rise with the elbows as fulcrum. Therefore, even where there is a bad habit of pulling the elbows backward, this correcting action allows the correcting of such a motion to a correct back swing. In the case of follow through, the same action is applied to the opposite upper arm, thus accomplishing the same correction.