A single stage centrifugal compression test device comprising: a rotary shaft extending in an axial direction; a bearing (3A, 3B) rotatably supporting the rotary shaft about an axis of the rotary shaft; a driving source that drives the rotary shaft around the axis; and one impeller fixed to an outer circumferential surface of the rotary shaft and configured to compress a fluid flowing from a first side in an axial direction to an outside in a radial direction while rotating together with the rotary shaft, the single stage centrifugal compression test device further comprises: a flow path forming section having an introduction flow path that includes an annular opening section facing toward the first side of the one impeller in the axial direction and guides a fluid from the outside in the radial direction toward the inside in the radial direction by extending inward in the radial direction after being curved from the annular opening section toward the inside in the radial direction, an inlet flow path connected to the introduction flow path and guiding the fluid to the one impeller from the first side in the axial direction,; and an inlet space forming section having an introduction opening section which is opened in a part in a circumferential direction and through which a fluid is introduced toward the inside in the radial direction at the first side of the introduction flow path in the axial direction, forming an annular shape about the axis, and to which a front end of the introduction flow path is connected, characterized in that the flow path forming section has an interstage inflow path extending from the outside toward the inside in the radial direction and connected to the inlet flow path at a second side of the introduction flow path in the axial direction. a rotary shaft extending in an axial direction; a bearing (3A, 3B) rotatably supporting the rotary shaft about an axis of the rotary shaft; a driving source that drives the rotary shaft around the axis; and one impeller fixed to an outer circumferential surface of the rotary shaft and configured to compress a fluid flowing from a first side in an axial direction to an outside in a radial direction while rotating together with the rotary shaft, the single stage centrifugal compression test device further comprises: a flow path forming section having an introduction flow path that includes an annular opening section facing toward the first side of the one impeller in the axial direction and guides a fluid from the outside in the radial direction toward the inside in the radial direction by extending inward in the radial direction after being curved from the annular opening section toward the inside in the radial direction, an inlet flow path connected to the introduction flow path and guiding the fluid to the one impeller from the first side in the axial direction,; and an inlet space forming section having an introduction opening section which is opened in a part in a circumferential direction and through which a fluid is introduced toward the inside in the radial direction at the first side of the introduction flow path in the axial direction, forming an annular shape about the axis, and to which a front end of the introduction flow path is connected, characterized in that the flow path forming section has an interstage inflow path extending from the outside toward the inside in the radial direction and connected to the inlet flow path at a second side of the introduction flow path in the axial direction. a flow path forming section having an introduction flow path that includes an annular opening section facing toward the first side of the one impeller in the axial direction and guides a fluid from the outside in the radial direction toward the inside in the radial direction by extending inward in the radial direction after being curved from the annular opening section toward the inside in the radial direction, an inlet flow path connected to the introduction flow path and guiding the fluid to the one impeller from the first side in the axial direction,; and an inlet space forming section having an introduction opening section which is opened in a part in a circumferential direction and through which a fluid is introduced toward the inside in the radial direction at the first side of the introduction flow path in the axial direction, forming an annular shape about the axis, and to which a front end of the introduction flow path is connected, characterized in that the flow path forming section has an interstage inflow path extending from the outside toward the inside in the radial direction and connected to the inlet flow path at a second side of the introduction flow path in the axial direction.