Abstract: An inner folding structure of lunch box mainly has a body made of a soft material, the body has a peripheral wall made of the soft material and defining an accommodating space by surrounding the accommodating space, and a bottom wall of the same material as the peripheral wall and integrally formed with the peripheral wall, one end of the peripheral wall is connected to the bottom wall, and another end of the peripheral wall is formed with an opening communicating with the accommodating space. A direction in which the opening extends toward the bottom wall is a supporting force direction, the peripheral wall has an inner surface facing the accommodating space, and an outer surface opposite to the inner surface, the inner surface is recessed with a plurality of folding grooves around the accommodating space, and the outer surface extends straight and flatly along the supporting force direction.