Method of controlling a gate valve

Particle scattering is suppressed only by controlling the gate valve in opening the gate valve with the internal pressure of the chamber being matched to the atmospheric pressure. A method of controlling a gate valve is characterized in that, in a gate valve that presses its valve body to an opening of a chamber by detecting a torque of a motor that drives the valve body, the method comprises the following steps: acquiring in advance a local maximum of the torque at the time of decompressing the inside of the chamber with the valve body closed under the atmospheric pressure, detecting the torque when a vent gas is being introduced into the chamber before returning the inside of the chamber to the atmospheric pressure for opening the valve body, opening the valve body when the torque exceeds the local maximum of the torque so that a clearance is created between the valve body and the opening of the chamber, and opening fully the valve body after the particles are discharged together with the gas inside the chamber.