A seal body 24 is formed annularly to have a fitted/fixed portion 25 airtightly fitted and fixed to a shoulder 22 in a turbine housing 1 formed facing a scroll passage 8 and have a clearance facing portion 27 facing an outer periphery of a turbine-housing-side exhaust introducing wall 9a with a clearance S, the clearance facing portion 27 being caused to be pressed against the exhaust introducing wall 9a due to a difference in fluid pressure between the clearance S and the scroll passage 8. Slipout preventive means 29 is formed on the fitted/fixed portion 25 of the seal body 24 for preventing the fitted/fixed portion 25 from slipping out of the shoulder 22.