To provide a disk type steam trap having a long service life without causing uneven wear on a valve disk.

A variable pressure chamber 3 is formed by fixing a lid 2 to a body 1 having an inlet 4 and an outlet 5. A jet hole 6 opened at the center of the variable pressure chamber 3 is provided to communicate between an inlet 4 and the variable pressure chamber 3. An annular groove 8 is formed on the outer circumference of a jet hole 6. While an inner ring valve seat 9 is formed between the jet hole 6 and annular groove 8, an outer ring valve seat 10 is formed on the outer circumference of the annular groove 8. A discharge hole 7 is provided from the annular groove 8 to communicate between the variable pressure chamber 3 and the outlet 5. A disk-like valve disk 11 which sits on or separates from the inner ring valve seat 9 and outer ring valve seat 10, is arranged in the variable pressure chamber 3. A guide rod 12 is attached to the lower part of the valve disk 11 and provided with a guide member 13 on the outer circumference thereof. In valve opening and closing of the valve disk 11, the inclination of the valve disk 11 is prevented through being guided by the guide member 13. As a result, the occurrence of uneven wear can be prevented.