Disclosed is a folding box, comprising a base (1) and two pairs of side plates opposite each other. A safe edge (10) is provided at the periphery of the base (1). The side plates are articulated to the base and can be folded relative to the base (1). The side plates are double smooth surfaced side plates and at least one pair of side plate lower edges are provided with a cavity. When a folding box (100) is upright, a pair of side plate lower edges are connected to the other pair of side plate lower edges so as to form a frame. The frame is articulated to the base (1) by means of a hinge, so as to form a reinforced component which prevents the base from sinking and prevents the safe edge from caving in. The folding box increases the cleaning efficiency, and improves the scenario of the base sinking when a box body is loaded, solves the problem of the damage and collision among goods of upper and lower layers due to the fact that the base is pressed down and sinks when multi-layer stacking of the folding box occurs, and meanwhile solves the safety risk in warehouse storage caused by the failure of stacking due to side plate deformation caused by multi-layer stacking of folding boxes and side plates being pressed when the box body has a smaller wall thickness and a higher folding ratio.