To provide a disc type steam trap not causing gaps between a valve disc, and the surface of the inner and outer ring valve seats.

A variable pressure chamber 3 is formed by a body 1 and a lid 2, a jet hole 6 is opened in a center in a variable pressure chamber 3 side of the body 1 to communicate an inlet 4 with the variable pressure chamber 3, an annular groove 7 is provided on an outer periphery of the jet hole 6, the inner ring valve seat 8 is formed between the jet hole 6 and the annular groove 7, the outer ring valve seat 9 is formed in an outer periphery of the annular groove 7, a discharge hole 10 is opened from the annular groove 7 to communicate an outlet 5 with the variable pressure chamber 3, a discoidal valve disc 11 carrying out separation and seating with respect to a valve seat face comprising the inner ring valve seat 8 and the outer ring valve seat 9 is disposed in the variable pressure chamber 3, an annular resistance groove 15 is formed on a valve seat face of the inner ring valve seat 8, and an annular resistance groove 16 is formed on a valve seat face of the outer ring valve seat 9.