An intermediate intake-type diaphragm (OG) in which an introduction flow channel , an intermediate suction flow channel , and a curved flow channel are defined, the introduction flow channel extending from a radially outer side of an axial line to a radially inner side to guide a first fluid (G1) toward an impeller rotating about the axial line, the intermediate suction flow channel being adjacent to the introduction flow channel and extending from the radially outer side of the axial line to the radially inner side to guide a second fluid (G2) toward the impeller , the curved flow channel being connected to downstream sides of the introduction flow channel and the intermediate suction flow channel and extending so that an inner surface is curved from a position of connection with the introduction flow channel toward one side in the direction of the axial line, and the curved flow channel guides the first fluid and the second fluid toward the impeller , the intermediate intake-type diaphragm (OG) comprising: a flow-regulating vane that is provided in the introduction flow channel to regulate the first fluid to flow along the radial direction; a guide vane that is provided in the intermediate suction flow channel and configured to regulate the second fluid to flow along the radial direction, and a partition wall that partitions the introduction flow channel and the intermediate suction flow channel in the direction of the axial line, wherein a radially inner end portion of the partition wall is located further on a radially inner side than a radially outer end portion of the flow-regulating vane and further on a radially outer side than a boundary between the introduction flow channel and the curved flow channel, wherein a radially inner end portion of the flow-regulating vane is located further on the radially outer side than the radially inner end portion of the partition wall, and wherein a position in the radial direction of a radially inner end portion of the guide vane is the same as a position in the radial direction of the radially inner end portion of the flow-regulating vane . a flow-regulating vane that is provided in the introduction flow channel to regulate the first fluid to flow along the radial direction; a guide vane that is provided in the intermediate suction flow channel and configured to regulate the second fluid to flow along the radial direction, and a partition wall that partitions the introduction flow channel and the intermediate suction flow channel in the direction of the axial line, wherein a radially inner end portion of the partition wall is located further on a radially inner side than a radially outer end portion of the flow-regulating vane and further on a radially outer side than a boundary between the introduction flow channel and the curved flow channel, wherein a radially inner end portion of the flow-regulating vane is located further on the radially outer side than the radially inner end portion of the partition wall, and wherein a position in the radial direction of a radially inner end portion of the guide vane is the same as a position in the radial direction of the radially inner end portion of the flow-regulating vane . <EOS>