PURPOSE: To provide a gate valve eliminating friction caused by the sliding, rolling, and the like of each constituent member in association with the opening/closing of a valve and dissolving the generation of dust inside a valve body.

CONSTITUTION: In addition to providing a valve opening/closing mechanism outside of a valve body 10, it is so constituted that the movement of a slide block 22 for transmitting the movement of the piston rod 21 of an air cylinder 20, fixed to a base plate 40, to the valve stem 51 so as to drive the valve stem 51 is along a guide rail 44 integral with the base plate 40. The runout of the valve stem 51 is thereby eliminated, and the valve body 10 is fitted to the valve stem 51 not through a movable part.