A centrifugal compressor, comprising: a housing including an intake-air inlet which opens in a direction of a rotational axis of the centrifugal compressor, and an intake-air channel which connects to the intake-air inlet; an impeller wheel disposed inside the housing rotatably around the rotational axis, and configured to compress intake gas which flows in from the intake-air inlet; and a swirl-flow generating unit (51, 93) disposed between the intake-air inlet and the impeller wheel inside the housing and configured to swirl the intake gas which flows in from the intake-air inlet, wherein the swirl-flow generating unit (51, 93) includes: a swirl-flow generating part (55, 96) which includes a plurality of guide vanes (55, 96) disposed in a circumferential direction along an inner circumferential wall of the housing and which is configured to swirl the intake gas flowing in from the intake-air inlet around the rotational axis by means of the plurality of guide vanes; and a central intake-air flow part which is a space surrounded by the swirl-flow generating part and which opens in the direction of the rotational axis so that the intake gas flowing in from the intake-air inlet passes through the central intake-air flow part, wherein the housing includes a recirculation flow path (41, 70, 98) which is disposed on an outer side of the intake-air channel and which brings an outer circumferential section of the impeller wheel into communication with the intake-air channel at an upstream side with respect to the impeller wheel, and wherein an opening end portion at an upstream side of the recirculation flow path is disposed upstream with respect to the swirl-flow generating unit (51, 93), and return flow air from the opening end portion at the upstream side of the recirculation flow path flows toward the guide vanes (55, 96) of the swirl-flow generating part, the centrifugal compressor being characterised in that the central intake-air flow part is formed by a ring circular member which is disposed concentric with the rotational axis and which has a hollow center, and in that the guide vanes (55, 96) are arranged in a circumferential direction on an outer circumferential side of the ring circular member. a housing including an intake-air inlet which opens in a direction of a rotational axis of the centrifugal compressor, and an intake-air channel which connects to the intake-air inlet; an impeller wheel disposed inside the housing rotatably around the rotational axis, and configured to compress intake gas which flows in from the intake-air inlet; and a swirl-flow generating unit (51, 93) disposed between the intake-air inlet and the impeller wheel inside the housing and configured to swirl the intake gas which flows in from the intake-air inlet, wherein the swirl-flow generating unit (51, 93) includes: a swirl-flow generating part (55, 96) which includes a plurality of guide vanes (55, 96) disposed in a circumferential direction along an inner circumferential wall of the housing and which is configured to swirl the intake gas flowing in from the intake-air inlet around the rotational axis by means of the plurality of guide vanes; and a central intake-air flow part which is a space surrounded by the swirl-flow generating part and which opens in the direction of the rotational axis so that the intake gas flowing in from the intake-air inlet passes through the central intake-air flow part, wherein the housing includes a recirculation flow path (41, 70, 98) which is disposed on an outer side of the intake-air channel and which brings an outer circumferential section of the impeller wheel into communication with the intake-air channel at an upstream side with respect to the impeller wheel, and wherein an opening end portion at an upstream side of the recirculation flow path is disposed upstream with respect to the swirl-flow generating unit (51, 93), and return flow air from the opening end portion at the upstream side of the recirculation flow path flows toward the guide vanes (55, 96) of the swirl-flow generating part, a swirl-flow generating part (55, 96) which includes a plurality of guide vanes (55, 96) disposed in a circumferential direction along an inner circumferential wall of the housing and which is configured to swirl the intake gas flowing in from the intake-air inlet around the rotational axis by means of the plurality of guide vanes; and a central intake-air flow part which is a space surrounded by the swirl-flow generating part and which opens in the direction of the rotational axis so that the intake gas flowing in from the intake-air inlet passes through the central intake-air flow part, wherein the housing includes a recirculation flow path (41, 70, 98) which is disposed on an outer side of the intake-air channel and which brings an outer circumferential section of the impeller wheel into communication with the intake-air channel at an upstream side with respect to the impeller wheel, and wherein an opening end portion at an upstream side of the recirculation flow path is disposed upstream with respect to the swirl-flow generating unit (51, 93), and return flow air from the opening end portion at the upstream side of the recirculation flow path flows toward the guide vanes (55, 96) of the swirl-flow generating part,