A rotary machine comprising: a nozzle configured to introduce a fluid from an outer circumferential side to an inner circumferential side in a radial direction; a volute having an inner space in communication with the nozzle at the outer circumferential side and a partition section configured to separate the inner space in a circumferential direction at an opposite side from a connection section connected to the nozzle with a central axis sandwiched therebetween; a guide section having a flow path in communication with the volute at the inner circumferential side of the volute, and being configured to guide the fluid introduced from the volute; and an impeller connected to the guide section in the axial direction and into which the fluid guided by the guide section is introduced, wherein the volute comprises: an annular opening section in communication with the guide section at the inner circumferential side of the space of the volute; and an inner wall surface extending from the opening section towards the impeller in the axial direction to increase a width dimension of the inner space of the volute in the axial direction and being connected to the partition section, wherein the guide section forms an annular first flow path in communication with the inner space of the volute at the inner circumferential side of the volute and extends toward the inner circumferential side, and a cylindrical second flow path extending from the inner circumferential side of the first flow path toward the downstream side along the axis O; wherein the inner wall surface has a dimension in the axis O direction gradually reduced in immediate front of the partition section and is connected to the partition section; wherein a plurality of vanes configured to guide the gas flowing in the circumferential direction of the suction volute toward the second flow path are disposed at the first flow path of the guide section; the rotary machine being characterised in that the vanes comprising inner circumferential vanes vertically installed at the inner circumferential side in the axis O direction toward the second flow path in the radial direction, and outer circumferential vanes vertically installed at the outer circumferential side than the inner circumferential vanes and angled toward the nozzle; the outer circumferential vanes are disposed at an intermediate position of the inner circumferential vanes in the circumferential direction. a nozzle configured to introduce a fluid from an outer circumferential side to an inner circumferential side in a radial direction; a volute having an inner space in communication with the nozzle at the outer circumferential side and a partition section configured to separate the inner space in a circumferential direction at an opposite side from a connection section connected to the nozzle with a central axis sandwiched therebetween; a guide section having a flow path in communication with the volute at the inner circumferential side of the volute, and being configured to guide the fluid introduced from the volute; and an impeller connected to the guide section in the axial direction and into which the fluid guided by the guide section is introduced, wherein the volute comprises: an annular opening section in communication with the guide section at the inner circumferential side of the space of the volute; and an inner wall surface extending from the opening section towards the impeller in the axial direction to increase a width dimension of the inner space of the volute in the axial direction and being connected to the partition section, wherein an annular opening section in communication with the guide section at the inner circumferential side of the space of the volute; and an inner wall surface extending from the opening section towards the impeller in the axial direction to increase a width dimension of the inner space of the volute in the axial direction and being connected to the partition section, wherein the guide section forms an annular first flow path in communication with the inner space of the volute at the inner circumferential side of the volute and extends toward the inner circumferential side, and a cylindrical second flow path extending from the inner circumferential side of the first flow path toward the downstream side along the axis O; wherein the inner wall surface has a dimension in the axis O direction gradually reduced in immediate front of the partition section and is connected to the partition section; wherein a plurality of vanes configured to guide the gas flowing in the circumferential direction of the suction volute toward the second flow path are disposed at the first flow path of the guide section; the rotary machine being characterised in that the vanes comprising inner circumferential vanes vertically installed at the inner circumferential side in the axis O direction toward the second flow path in the radial direction, and outer circumferential vanes vertically installed at the outer circumferential side than the inner circumferential vanes and angled toward the nozzle; the outer circumferential vanes are disposed at an intermediate position of the inner circumferential vanes in the circumferential direction.