To provide a pilot type steam trap capable of surely opening and closing a pilot valve orifice and not leaking steam.

This steam trap comprises a main body 1 forming an inlet passage 4, an outlet passage 5 and a valve port 7 establishing communication between both passages, a metal diaphragm 8 arranged to oppose to the valve port 7 from an inlet passage 4 side and opening and closing the valve port 7 by bending according to pressure fluctuation, a pressure chamber 14 formed by an inner cover 12 wall and the metal diaphragm 8, a pilot valve orifice 15 provided with passing through the inner cover 12 to establish communication between the inlet passage 4 and the pressure chamber 14, a bimetal valve 16 closing the pilot valve orifice 15 at low temperature and opening the same at high temperature, and a communication small hole 18 provided on the metal diaphragm 8 with passing through the same to establish communication between the pressure chamber 14 and the outlet passage 5 and having a smaller diameter than the pilot valve orifice 15.