A high-temperature component according to an embodiment is a high-temperature component which requires cooling by a cooling medium, and includes: a plurality of cooling passages through which the cooling medium is able to flow; a header portion to which downstream ends of the plurality of first cooling passages are connected; and at least one outlet passage for discharging the cooling medium flowing into the header portion to outside of the header portion. A roughness of an inner wall surface of the at least one outlet passage is not greater than a roughness of an inner wall surface of the plurality of first cooling passages in a region where a flow-passage cross-sectional area of the outlet passage is the smallest.