A centrifugal compressor comprising: an impeller which includes a hub and a plurality of centrifugal blades attached to the outer peripheral surface of the hub; and a casing which rotatably accommodates the impeller, wherein the casing includes: a suction flow path through which a fluid sucked from the outside by rotation of the impeller is introduced to the impeller; a diffuser part which is annularly formed on an outer peripheral side of the impeller, and decelerates the flow of the fluid discharged to the outer peripheral side by the rotation of the impeller; a spiral volute part which is formed on an outer peripheral side of the diffuser part and in which a cross-sectional area is gradually increased along a circumferential direction; a discharge pipe which extends from a part having the largest cross-section area of the volute part toward the outer peripheral side; and a connecting part which is formed on a side wall surface of a diffuser flow path through which the fluid flows in the diffuser part, and causes the inner portion of the volute part and the inner portion of the diffuser flow path to communicate with each other, and wherein an opening part of the diffuser flow path side of the connecting part is formed on a downstream side of the diffuser flow path, the centrifugal compressor being characterized in that said opening part is formed in only a region from within 30° of a upstream side of the diffuser part to within 30° of a downstream side thereof based on a tongue which is formed between a minimum area part of the volute part and the discharge pipe. an impeller which includes a hub and a plurality of centrifugal blades attached to the outer peripheral surface of the hub; and a casing which rotatably accommodates the impeller, wherein the casing includes: a suction flow path through which a fluid sucked from the outside by rotation of the impeller is introduced to the impeller; a diffuser part which is annularly formed on an outer peripheral side of the impeller, and decelerates the flow of the fluid discharged to the outer peripheral side by the rotation of the impeller; a spiral volute part which is formed on an outer peripheral side of the diffuser part and in which a cross-sectional area is gradually increased along a circumferential direction; a discharge pipe which extends from a part having the largest cross-section area of the volute part toward the outer peripheral side; and a connecting part which is formed on a side wall surface of a diffuser flow path through which the fluid flows in the diffuser part, and causes the inner portion of the volute part and the inner portion of the diffuser flow path to communicate with each other, and wherein an opening part of the diffuser flow path side of the connecting part is formed on a downstream side of the diffuser flow path, the centrifugal compressor being characterized in that said opening part is formed in only a region from within 30° of a upstream side of the diffuser part to within 30° of a downstream side thereof based on a tongue which is formed between a minimum area part of the volute part and the discharge pipe. a suction flow path through which a fluid sucked from the outside by rotation of the impeller is introduced to the impeller; a diffuser part which is annularly formed on an outer peripheral side of the impeller, and decelerates the flow of the fluid discharged to the outer peripheral side by the rotation of the impeller; a spiral volute part which is formed on an outer peripheral side of the diffuser part and in which a cross-sectional area is gradually increased along a circumferential direction; a discharge pipe which extends from a part having the largest cross-section area of the volute part toward the outer peripheral side; and a connecting part which is formed on a side wall surface of a diffuser flow path through which the fluid flows in the diffuser part, and causes the inner portion of the volute part and the inner portion of the diffuser flow path to communicate with each other, and wherein an opening part of the diffuser flow path side of the connecting part is formed on a downstream side of the diffuser flow path, the centrifugal compressor being characterized in that said opening part is formed in only a region from within 30° of a upstream side of the diffuser part to within 30° of a downstream side thereof based on a tongue which is formed between a minimum area part of the volute part and the discharge pipe.