To solve the problem that skillfulness is obtained by lots of practices since it is difficult to excellently give a body weight or a force to the rear end of a board when the body weight is transferred because of a horizontal bottom surface in a conventional ski, a snowboard and a surfboard, etc.

A projected part is fitted to the center part of the bottom surface of the ski, the snowboard and the surfboard, etc., so as to be broader from a rear part toward a front part as a weight transfer guide device. Then the body weight is easily transferred so that the body weight and the force are excellently transferred to the rear end part of the board such as the ski, the snowboard and the surfboard.