An on-off valve device (8, 30, 40, 50, 60) comprising a suction flow path to supply a fluid which leads from an inflow port of a housing covering a turbine rotor blade to a scroll portion and is configured of a single piece or multiple divided pieces with an inner surface of the suction flow path formed using a first wall surface (17, 83, 95) and a second wall surface (18, 85, 96) facing the first wall surface (17, 83, 95) as a portion of the suction flow path, a valve body (10, 32, 42, 52, 62), which extends from the upstream side toward the downstream side of the flow of the fluid, is rotatably provided in a direction toward and away from the first wall surface (17, 83, 95) and the second wall surface (18, 85, 96), forms an upstream-side narrowed flow path between the first wall surface (17, 83, 95) and the valve body (10, 32, 42, 52, 62) at an end on the upstream side, and forms a downstream-side narrowed flow path between the second wall surface (18, 85, 96) and the valve body (10, 32, 42, 52, 62) at an end on the downstream side, and a rotary portion (11; 63) configured to rotate the valve body (10; 32; 42; 52; 62) about an axis which is a rotation center of the valve body (10; 32; 42; 52; 62), wherein the valve body (10, 32, 42, 52, 62) includes a first surface (21, 33, 43, 53) facing the first wall surface (17, 83, 95) and a second surface (22, 34, 44, 54) facing the second wall surface (18, 85, 96), the first surface (21, 33, 43, 53) of the valve body (10, 32, 42, 52, 62) has a protrusion shape toward the first wall surface (17, 83, 95), the valve body (10, 32, 42, 52, 62) is fully opened when the first surface (21; 33; 43; 53) is parallel to the first wall surface (17; 83, 95), the valve body (10, 32, 42, 52, 62) is fully closed when a front edge portion (10a, 32a, 42a, 52a) of the valve body (10, 32, 42, 52, 62) comes into contact with the first wall surface (17; 83; 95) along with a rear edge portion (10b, 32b, 42b, 52b) comes into contact with the second wall surface (18; 85; 96), the opening degree of the valve body (10, 32, 42, 52, 62) is indicated as an inclination angle (θ) of the rear edge portion (10b, 32b, 42b, 52b) of the valve body (10, 32, 42, 52, 62) in a direction from the first wall surface (17; 83; 95) to the second wall surface (18; 85; 96), in an intermediate opening condition of the valve body (10, 32, 42, 52, 62) between a fully close condition and a fully open condition of the valve body (10, 32, 42, 52, 62), the front edge portion (10a, 32a, 42a, 52a) of the valve body (10, 32, 42, 52, 62) approaches the first wall surface (17; 83; 95) and the rear edge portion (10b, 32b, 42b, 52b) approaches the second wall surface (18; 85; 96), the width of the upstream-side narrowed flow path decreases according to the shape of the first surface of the valve body (10, 32, 42, 52, 62), and thereafter the flow path width gradually increases in a flow direction of the fluid, and the on-off valve device (8; 30; 40; 50; 60) is characterized in that the axis of the rotary portion (11; 63) is positioned outside the valve body (10; 32; 42; 52; 62). extends from the upstream side toward the downstream side of the flow of the fluid, is rotatably provided in a direction toward and away from the first wall surface (17, 83, 95) and the second wall surface (18, 85, 96), forms an upstream-side narrowed flow path between the first wall surface (17, 83, 95) and the valve body (10, 32, 42, 52, 62) at an end on the upstream side, and forms a downstream-side narrowed flow path between the second wall surface (18, 85, 96) and the valve body (10, 32, 42, 52, 62) at an end on the downstream side, and a rotary portion (11; 63) configured to rotate the valve body (10; 32; 42; 52; 62) about an axis which is a rotation center of the valve body (10; 32; 42; 52; 62), wherein the valve body (10, 32, 42, 52, 62) is fully closed when a front edge portion (10a, 32a, 42a, 52a) of the valve body (10, 32, 42, 52, 62) comes into contact with the first wall surface (17; 83; 95) along with a rear edge portion (10b, 32b, 42b, 52b) comes into contact with the second wall surface (18; 85; 96), the opening degree of the valve body (10, 32, 42, 52, 62) is indicated as an inclination angle (θ) of the rear edge portion (10b, 32b, 42b, 52b) of the valve body (10, 32, 42, 52, 62) in a direction from the first wall surface (17; 83; 95) to the second wall surface (18; 85; 96), in an intermediate opening condition of the valve body (10, 32, 42, 52, 62) between a fully close condition and a fully open condition of the valve body (10, 32, 42, 52, 62), the front edge portion (10a, 32a, 42a, 52a) of the valve body (10, 32, 42, 52, 62) approaches the first wall surface (17; 83; 95) and the rear edge portion (10b, 32b, 42b, 52b) approaches the second wall surface (18; 85; 96), the width of the upstream-side narrowed flow path decreases according to the shape of the first surface of the valve body (10, 32, 42, 52, 62), and thereafter the flow path width gradually increases in a flow direction of the fluid, and