Compressor and gas turbine

A compressor includes a rotor including a plurality of disks, a shaft portion connected on a downstream side of the disks; and rotor blade rows fixed to the plurality of disks; a stator including a compressor casing; and a plurality of stator vane rows each provided between corresponding adjacent ones of the rotor blade rows; an outlet guide vane including blade main bodies disposed at an interval in a circumferential direction on the downstream side of the disk located most downstream, and inner shrouds connecting the blade main bodies in the circumferential direction, on an inner side in a radial direction; and an inner casing disposed on the downstream side of the disk located most downstream with a gap between the disk and the inner casing. The inner casing includes an outer peripheral wall surface having recesses accommodating the inner shrouds and forming, together with an inside surface of the compressor casing, a diffuser on the downstream side of the recesses, and an inner peripheral wall surface forming an air extraction cavity. An air extraction hole is formed in a portion, in the recesses, on the downstream side.