An axial compressor comprising liquid drop feed means for feeding liquid drops to an operating fluid of the compressor (1), a casing (54) for forming a flow path through which the operating fluid flows down and a plurality of stages, each of which is composed of one continuous rotor blade row (51) and one continuous stator vane row (53), the axial compressor (1) being structured so that the liquid drops evaporate inside the compressor (1), wherein the casing (54) is provided with a cavity (64) therein, and the cavity (64) is formed by an outer casing (62) and an inner casing (63) which is enclosing a periphery of the rotor blade rows (51) at the plurality of stages and forming internally a flow path of the operating fluid, and a flow path is provided for feeding the operating fluid to the cavity (64) on a downstream side of a region forming the cavity (64) of the inner casing (63).