PURPOSE: A cutoff valve is provided to make installation and maintenance easy and to apply to a large-diameter pipeline. CONSTITUTION: A cutoff valve(100) contains: a lower body(110) formed in a cylindrical shape having a hollow inside and provided with an inflow port to let fluids flow in and a discharge port to discharge influent fluids; an upper body(120) connected to the upper part of the lower body; a wafer(130) installed between the inflow port and the discharge port to cut off the flow of fluids by rotation; a worm gear(140) connected vertically to the top of the wafer and located in the upper body; a pinion gear(160) fixed to the upper body to be rotatable to transfer rotary power to the worm gear; a rack gear(150) engaged with the pinion gear to move horizontally; and a pneumatic cylinder(170) installed to the end of the rack gear to make the horizontal movement of the rack gear possible.
