PURPOSE: To provide a suction box for vacuum forming in which a pattern plate is able to change easily, by providing an insertable pin at a lower side wall of a frame provided with a vertical through hole portion, forming a suction port at a side wall and a seal member at the outer circumference of the lower face of a bottom plate.

CONSTITUTION: Flange portions 1b, 1c are formed projecting on the inner and outer peripheries at the upper end position of a frame body 1 having a vertical through hollow portion 1a with the upper end having a slightly reduced diameter. A pair of movable pins 6 are formed at opposing positions on the lower portion of a side wall of the frame body 1 so as to be able to move in-and-out toward the hollow portion and a suction port is formed at the side wall. A pattern plate (model plate) 10 is inserted into the frame body 1 and a bottom plate 8 is fitted to the body 1. In order to hold them, the pin 6 is inserted into a cavity 8a formed in the side wall of the bottom plate 8. On the outer periphery of the bottom plate 8, a seal member 9 is formed so as to extend outwardly.