To provide opening-closing legs which can be folded and which has good stability and structural strength though which has a simple formation, and a ready-to-assemble table using the legs.

Two pairs of leg frames are provided which has horizontal frames between two columns. The horizontal frames of the leg frames are arranged one above the other like X-shape, and axes of rotation are provided at cross points. The two pairs of leg frames can be relatively opened and closed, and be folded. On upper points than the upper horizontal frames in the columns, insertion grooves having a certain depth are provided, so that horizontal shelf plates can be attached and removed when the leg frames are folded. The axes of rotation are inserted in the lower horizontal frames from beneath and threadable mounted on the upper horizontal frames by screws. Further, angle keeping devices which can be fixed by the screws are provided at the cross points of the horizontal frames. The angle keeping devices are jogged like a U shape so that the lower horizontal frames can be held from beneath, and depressed portions are formed so that the upper horizontal frames can be engaged with the lower horizontal frames at a certain angle at upper edges.