Abstract: Provided is a steam trap, in which an inlet and an outlet in a body are formed collinearily and a float for opening/closing the outlet is included. The steam trap having a float within a case includes the case, a cover, a strainer, the float, an arm, a gate, a lever, and a valve plug. The case includes therein an inlet through which condensate and water flow in and an outlet through which the condensate flow out. The cover is bolt-coupled to the case. The strainer is formed in the inlet and filters foreign substances. The float is formed within the case. The arm is formed at the bottom of the float. The gate is screw-engaged with one side of the case and has an orifice formed therein. The lever connects the gate and the arm. The valve plug is formed in the lever and opens and closes the outlet.