A plastic soap box comprises a box body and a base plate. The base plate comprises a left plate unit and a right plate unit; the left plate unit is connected to a rotary shaft of the bottom of the left wall of the box body; the right plate unit is connected to the rotary shaft of the bottom of the right wall of the box body; the surfaces of the left and right plate units adjacent to the connections of the side walls of the box body are provided with triggering buckles respectively; spring grooves are arranged on the outer walls of two sides of the box body and are provided with twisting springs respectively, and two ends of the twisting springs are fixedly connected to the adjacent triggering bucklers and the side walls of the box body; two supporting rods are arranged between two side walls of the box body, and a plurality of supporting beams are arranged between the supporting rods; a sealing bar is arranged at the tail end of the left plate unit. The plastic soap box has the advantages that the box is simple in structure and convenient to use, owing to the integral structure, the soap liquid in the plastic soap box can be removed effectively, the interior of the soap box is simple and convenient to clean, and the cleanness of the surrounding is maintained effectively.