A scroll passage of a turbine housing includes: an outer peripheral surface extending along an axial direction of the turbine housing; an inner peripheral surface disposed inward of the outer peripheral surface; a one-side surface extending along the radial direction; an other-side surface disposed closer to an outlet of the housing; a one-side outer peripheral R portion connecting the one-side surface and the outer peripheral surface; an other-side outer peripheral R portion connecting the other-side surface and the outer peripheral surface; and an other-side inner peripheral R portion connecting the other-side surface and the inner peripheral surface. A ratio of a width dimension of the scroll passage to an R dimension of each portion is defined as a peripheral R ratio, and the peripheral R ratio has an R ratio increasing region the ratio increases from upstream to downstream in the scroll passage.