A turbine comprising: a rotor that is rotatably supported; a casing that is provided around the rotor; a blade body (40,50) having a blade (49, 59) and a shroud (41, 51), the blade being provided at one of the rotor and the casing and extending in a radial direction toward the other side from one side, the shroud (41,51) extending in a circumferential direction at a tip portion in the radial direction of the blade; and an annular groove provided at the other of the rotor and the casing, extending in the circumferential direction, accommodating the shroud (41,51) with a gap interposed therebetween, and relatively rotating with respect to the blade body (40,50); wherein leakage flow leaked from main flow flowing along the blade flows into the gap; wherein the shroud (41,51) includes a peripheral surface (43C, 53C), a curved guide surface (47,57,57A), and a trailing edge end portion (46, 56, 70), the peripheral surface (43C, 53C) facing the annular groove, the trailing edge end portion (46,56,70) being formed closer to the main flow side than the peripheral surface (43c,53c) in a downstream side of the leakage flow, the curved guide surface being formed between the peripheral surface (43C, 53C) and the trailing edge end portion (46, 56, 70), and wherein the curved guide surface (47,57,57A) is configured to guide the leakage flow along the peripheral surface from the peripheral surface (43c,53c) to the trailing edge end portion (46,56,70), characterized in that the curved guide surface (47, 57, 57A) has a convex shape protruding outward toward the annular groove and away from the blade and the convex shape being selected from the group consisting of a quarter arc shape, a quarter elliptical shape, and a shape of a part of an elliptical outer periphery in a cross-sectional contour of a cross-section intersecting the circumferential direction. a rotor that is rotatably supported; a casing that is provided around the rotor; a blade body (40,50) having a blade (49, 59) and a shroud (41, 51), the blade being provided at one of the rotor and the casing and extending in a radial direction toward the other side from one side, the shroud (41,51) extending in a circumferential direction at a tip portion in the radial direction of the blade; and an annular groove provided at the other of the rotor and the casing, extending in the circumferential direction, accommodating the shroud (41,51) with a gap interposed therebetween, and relatively rotating with respect to the blade body (40,50); wherein leakage flow leaked from main flow flowing along the blade flows into the gap; wherein the shroud (41,51) includes a peripheral surface (43C, 53C), a curved guide surface (47,57,57A), and a trailing edge end portion (46, 56, 70), the peripheral surface (43C, 53C) facing the annular groove, the trailing edge end portion (46,56,70) being formed closer to the main flow side than the peripheral surface (43c,53c) in a downstream side of the leakage flow, the curved guide surface being formed between the peripheral surface (43C, 53C) and the trailing edge end portion (46, 56, 70), and wherein the curved guide surface (47,57,57A) is configured to guide the leakage flow along the peripheral surface from the peripheral surface (43c,53c) to the trailing edge end portion (46,56,70), characterized in that the curved guide surface (47, 57, 57A) has a convex shape protruding outward toward the annular groove and away from the blade and the convex shape being selected from the group consisting of a quarter arc shape, a quarter elliptical shape, and a shape of a part of an elliptical outer periphery in a cross-sectional contour of a cross-section intersecting the circumferential direction.