Provided is a valve for vacuum process, including: a first valve body having an inlet port and an outlet port; a sealing unit configured to move forward to and backward from the inlet port so as to have a closed position and an open position; a shaft covered with a bellows, and configured to move the sealing unit between the closed position and the open position; a cover for shielding the bellows from corrosive gas when the sealing unit is in the open position; and a cover guide unit configured to guide the cover to move along the shaft.