To provide an auxiliary step board, with which the movement of a weight can be easily physically felt, in the main body of buck to freely house it by attaching the auxiliary step board to the main body of buck to freely rotate it between a using position expanded outside almost horizontally to a side face and a housing position for almost horizontally folding the board in an inside hollow.

An auxiliary step board 2 is composed of an attaching part 6 to be mounted inside a step 3 in the main body of buck and a hinge part 8 for expanding or housing a step part 7 of a foot placing portion into horizontal attitude. Namely, the attaching part 6 is composed of a block body forming an upper wall surface into horizontal surface, forming an inside wall surface into vertical surface and setting an outside wall surface into slot tightly in contact with the inclination of the side plate of the step 3. Therefore, at the time of expansion, the step part 7 engages a base side on the upper wall surface of the attaching part 6, regulates the rotation of the hinge part 8 and maintains an outward horizontal attitude. At the time of folding, the step part is rotated at 180°, engages the other attaching plate of the hinge part 8 with the inside wall surface of the attaching part 6, regulates the rotation of the hinge part 8 and maintains an inward horizontal attitude.