To regulate the height of an X-shaped collapsible leg itself by extending by connecting extension members to the tubular legs or storing the extension members into the tubular legs and solve the difficulty of miniaturization.

Two legs 1 and 2 are connected by movable fulcrum joints 3 having fulcrums of the pins 3C. The legs 1 and 2 are swiveled by operating integrally with joint frames 3a and 3b around pins 3c. By moving the joints 3 on the legs 1 and 2, the spread of the legs can be kept constantly and the height can be regulated. As tubular legs 1 and 2 have no obstacle such as pins, extension members 4 can be extended by a length almost equivalent to the length of the legs 1 and 2, and can stored without modifying the extension members 4.