SCROLL EXPANDER

PROBLEM TO BE SOLVED: To prevent decrease in a service life due to wear by improving wear resistance in a sealing member of a scroll expander.SOLUTION: A scroll expander includes: a fixed scroll 2 having a spiral wrap 5 that stands on an end face of a fixed end plate; and an orbiting scroll disposed to oppose to the fixed scroll 2 and having a spiral wrap that stands on an end face of an orbiting end plate to segment a plurality of expansion chambers between the orbiting scroll wrap and the wrap 5 of the fixed scroll 2. Each wrap has a recessed groove 5a formed therein as extending along the top end of the wrap 5; and a sealing member 16 is mounted in the recessed groove 5a, wherein the sealing member is configured to slide on an inner face of the counter end plate. The scroll expander rotates the orbiting scroll by expansion of a working medium flowing into the expansion chambers. Each recessed groove 5a is formed in such a manner that the depth gradually increases from an inner circumferential end side to an outer circumferential end side; and each sealing member 16 is formed in such a manner the thickness gradually increases along the spiral recessed groove from the inner circumferential end side to the outer circumferential end side.