To provide a float type steam trap quickly discharging a large quantity of air.

A valve seat 9 in which a valve hole 7 and an orifice 8 are arranged is coupled to a lid 2 of a sidewall in the lower side of a valve chamber 3. The valve hole 7 is opened directed obliquely downward. A valve chamber side opening comes closer to the valve chamber side opening of the valve hole 7 and is opened above the valve chamber side opening of the valve hole 7 in the orifice 8. A float 11 opening and closing the valve hole 7 is arranged in the valve chamber 3. A bimetal 13 having a substantial U-shape cross-section as a temperature responding member is arranged in the valve chamber 3. The bimetal 13 deforms such that the U-shape is narrowed, does not interfere with the float 11, reduces the opening area of the orifice 8, at high temperature, and deforms such that the U-shape is widened, increases the opening area of the orifice 8, lifts the float 11, and opens the valve hole 7, at low temperature. The opening area of the orifice 8 at the high temperature is formed in a size so as not to be able to discharge condensed water generated during usual operation where steam is sent to a steam piping system.