A gas compressor, comprising: a hollow cylinder member; a rotor rotatably disposed inside the cylinder member; a plurality of vanes attached to the rotor in a projectable and houseable manner, the plurality of vanes including leading ends which have contact with an inner circumferential surface of the cylinder member, so as to form a plurality of compression rooms inside the cylinder member, wherein a cylinder room which changes a volume of the compression room, and performs a gas compression cycle is formed between the cylinder member and the rotor, a suction section which sucks the gas is provided upstream of the cylinder room, a discharge section which discharges the gas is provided downstream of the cylinder room, a proximal section in which the cylinder member and the rotor come close to each other is provided in one position between the cylinder member and the rotor, so that a single cylinder room which performs the gas compression cycle one-time per one cycle for each compression room is formed, the cylinder room has an asymmetric shape such that a distant section having a maximum distance between the inner circumferential surface of the cylinder member and an outer circumferential surface of the rotor is located upstream of a position to which the proximal section faces across a rotation center of the rotor in a rotation direction, at least one sub-discharge section, which maintains discharge pressure of the gas by releasing pressure of the compression room when the pressure of the gas in the compression room reaches the discharge pressure, is provided upstream of the discharge section, and the sub-discharge section is disposed relative to an adjacent discharge section to have an interval which is the same as an interval between the leading ends of the adjacent two vanes or an interval narrower than that, and is formed in a position closer to the vane provided upstream of the rotation direction than the vane provided downstream of the rotation direction in a state in which the vane provided downstream of the rotation direction forming the compression room faces the discharge section. a hollow cylinder member; a rotor rotatably disposed inside the cylinder member; a plurality of vanes attached to the rotor in a projectable and houseable manner, the plurality of vanes including leading ends which have contact with an inner circumferential surface of the cylinder member, so as to form a plurality of compression rooms inside the cylinder member, wherein a cylinder room which changes a volume of the compression room, and performs a gas compression cycle is formed between the cylinder member and the rotor, a suction section which sucks the gas is provided upstream of the cylinder room, a discharge section which discharges the gas is provided downstream of the cylinder room, a proximal section in which the cylinder member and the rotor come close to each other is provided in one position between the cylinder member and the rotor, so that a single cylinder room which performs the gas compression cycle one-time per one cycle for each compression room is formed, the cylinder room has an asymmetric shape such that a distant section having a maximum distance between the inner circumferential surface of the cylinder member and an outer circumferential surface of the rotor is located upstream of a position to which the proximal section faces across a rotation center of the rotor in a rotation direction, at least one sub-discharge section, which maintains discharge pressure of the gas by releasing pressure of the compression room when the pressure of the gas in the compression room reaches the discharge pressure, is provided upstream of the discharge section, and the sub-discharge section is disposed relative to an adjacent discharge section to have an interval which is the same as an interval between the leading ends of the adjacent two vanes or an interval narrower than that, and is formed in a position closer to the vane provided upstream of the rotation direction than the vane provided downstream of the rotation direction in a state in which the vane provided downstream of the rotation direction forming the compression room faces the discharge section.