To provide a float-type steam trap capable of discharging a specified amount of drain from a normal-opened orifice without any relation of a pressure difference between the inlet side and the outlet side.

An inlet 2 is fixed to an upper part of a valve casing 1 and an outlet 3 is fixed to a lower part of the valve casing 1 and a valve chamber 4 is formed within the valve casing. A normal-opened orifice 5 is arranged at the lower part of the valve chamber 4 integral with the outlet 3. The lower end of the orifice 5 is communicated with an outlet passage 6 formed at the outlet 3. A specified flow rate valve mechanism 7 formed by a resilient member is attached to the upper end of the orifice 5. A variable passage 8 is formed at the central part of the specified flow rate valve mechanism 7. The variable passage 8 has the state shown in Fig.1 corresponding to the maximum passage area, and as a pressure difference between the inlet 2 side and the outlet 3 side is increased, the specified flow rate valve mechanism 7 formed by the resilient member is deformed downwardly to cause the passage area of the variable passage 8 to be gradually decreased, resulting in that a specified amount of drain can be discharged without any relation with a pressure difference between the inlet 2 side and the outlet 3 side.