A gate valve having a disk replacement structure and disposed in a piping, the gate valve comprising: a valve body including a blocking space formed therein, a pair of flange pipes provided to communicate with the blocking space, and a cover coupled to an upper portion of the valve body to close the blocking space; a disk provided to be lifted up and down in the blocking space and including a coupling hole in an upper portion of which a lifting nut is disposed; and an operating rod disposed in the cover and configured to move the disk up and down, wherein the cover is provided with an insertion hole to penetrate through the cover, and the operating rod is rotatably disposed in the insertion hole, wherein the valve body is provided with a fixing member configured to support and fix the disk, and characterized in that the disk is provided with engaging grooves having an upper inclined surface and a lower inclined surface on both side surfaces or front and rear surfaces to be pressed and fixed by the fixing member, wherein the disk is further provided with support slopes on both sides of an upper portion thereof to be pressed and fixed by the fixing member, and wherein the fixing member comprises a pair of fastening holes formed in the valve body in an oblique direction and communicating with the blocking space, fixing tubes inserted into and fixed to the fastening holes and having a threaded portion formed on an inner circumferential surface thereof, and pressing rods which are screwed with the fixing tubes and press the disk by rotation, and wherein the lifting nut is disposed on an upper portion of the coupling hole, wherein the disk is moved upward by a forward rotation of the operating rod screwed with the lifting nut so that the flange pipes are opened and the operating rod is inserted into a lower portion of the coupling hole, and wherein when the operating rod is rotated in a reverse direction, the disk is moved downward while closing the flange pipes. a valve body including a blocking space formed therein, a pair of flange pipes provided to communicate with the blocking space, and a cover coupled to an upper portion of the valve body to close the blocking space; a disk provided to be lifted up and down in the blocking space and including a coupling hole in an upper portion of which a lifting nut is disposed; and an operating rod disposed in the cover and configured to move the disk up and down, wherein the cover is provided with an insertion hole to penetrate through the cover, and the operating rod is rotatably disposed in the insertion hole, wherein the valve body is provided with a fixing member configured to support and fix the disk, and characterized in that the disk is provided with engaging grooves having an upper inclined surface and a lower inclined surface on both side surfaces or front and rear surfaces to be pressed and fixed by the fixing member, wherein the disk is further provided with support slopes on both sides of an upper portion thereof to be pressed and fixed by the fixing member, and wherein the fixing member comprises a pair of fastening holes formed in the valve body in an oblique direction and communicating with the blocking space, fixing tubes inserted into and fixed to the fastening holes and having a threaded portion formed on an inner circumferential surface thereof, and pressing rods which are screwed with the fixing tubes and press the disk by rotation, and wherein the lifting nut is disposed on an upper portion of the coupling hole, wherein the disk is moved upward by a forward rotation of the operating rod screwed with the lifting nut so that the flange pipes are opened and the operating rod is inserted into a lower portion of the coupling hole, and wherein when the operating rod is rotated in a reverse direction, the disk is moved downward while closing the flange pipes.