A turbine includes a housing including an inlet, an outlet, and a shroud section having a shroud surface extending between the inlet and the outlet; and a turbine impeller housed in the housing and including a hub and a plurality of blades disposed on an outer peripheral surface of the hub, each of the blades having a side edge extending along the shroud surface. The side edge of each of the blades has a side-edge upstream portion disposed on a side of the inlet, and a side-edge downstream portion disposed on a side of the outlet. The shroud surface has a shroud upstream portion disposed on the side of the inlet and extending along the side-edge upstream portion, and a shroud downstream portion disposed on the side of the outlet and extending along the side-edge downstream portion. The shroud upstream portion has a meridional cross-sectional shape whose inclination angle (θ1) with respect to an axis (L) of the hub at the side of the inlet is smaller than in a case where the shroud upstream portion has a meridional cross-sectional shape of an arc shape and the shroud downstream portion has a meridional cross-sectional shape of a linear shape along a direction of the axis of the hub.