To provide a foldable leg portion structure which folds and raises a leg portion securely and stably.

In the foldable leg portion structure for holding the leg portion pivoted at the top in a folded and raised state through a lock device, the leg portion of substantially U-shape is composed of: a crossbeam shaft portion linearly extending as a rotary shaft; a pair of L-shaped joints fitted and fixed at both ends of the crossbeam shaft portion; and leg supports fitted and fixed at the pair of the L-shaped joints. A pair of leg portion fixing bands for rotatably bearing the cross beam shaft portion are provided apart at both ends of the crossbeam and disposed so as to bring the inside of the L-shaped joint portion into contact with the outside of the leg fixing band. And the leg supports are positioned so as to prevent sidewise slip thereof.