The invention relates to a sewage inlet/exhaust valve, specifically to an inlet/exhaust valve for sewage containing lots of impurities and gases. The exhaust valve is provided with a gas vent having an enlarged size, which is advantageous for the exhausting of a large quantity of gases in the sewage, and simultaneously capable of preventing blockage; the gas vent is under the protection of a guide rod on a floating ball without contacting with bubbles easily incrusted in the sewage gases, thereby reducing blockage and ensuring long-term operation; besides, the position of the floating ball is in the middle position, so that the diameter of the whole valve body is reduced; and a circular floating ball is employed so that the contact area thereof with the liquid level can be widened and the length of the valve body can be also reduced. The exhaust valve overcomes the defects of impurity blockage and low gas output caused by a small gas outlet of the existing sewage inlet/exhaust valve.