PURPOSE: To speedily discharge condensed water and hence to keep a heating efficiency at the maximum level by providing a control unit for generating a control signal of opening and closing a valve means on the basis of a signal from a conversion section for obtaining a saturated temperature converted from a pressure and a signal from a temperature detecting means.

CONSTITUTION: A steam trap device is composed of a valve means 2 disposed on a secondary side of a steam using equipment 1, a pressure sensor 3 attached on a primary side of the valve means 2, a temperature sensor 4, and a control unit 5 containing a conversion section for converting the pressure signal from the pressure sensor 3. When condensed water in a steam trap 6 cannot be discharged, a pressure in a pipe is detected by a pressure sensor 3, and a saturated temperature at the pressure is obtained in the conversion section of the control unit 5. A temperature detected in the temperature sensor 4 is compared with the saturated temperature. Thus, when the detected temperature is under the saturated temperature, a control signal of opening the valve is transmitted from the control unit 5 to the valve means 2, to thus discharge the condensed water. Therefore, it is possible to speedily discharge the condensed water without staying irrespective of the amount of the condensed water.