Abstract: A straight trap toilet apparatus mainly comprises a main body with a straight trap, a piston, and a toilet bowl. The water outlet of the main body is connected to a waste pipe, and the top of the main body is mounted below the toilet bowl. The main body has a water valve, wherein one end of the water valve is connected to an inlet tube connected to a water-faucet, and the other end of the water valve is connected to an outlet tube that corresponds to the spurt water hole of the toilet bowl. In normal condition, water flows from the outlet tube into the toilet bowel and the main body. A water tank is in fluid communication with the main body by a linking tube such that the water in the toilet bowel and the water tank are at the same level. The motion of the float ball will control a valve handle to control the water valve for controlling the water intake. The water from the outlet tube may gather together in the main body, the toilet bowel, and is in fluid communication with the water tank by a linking tube.