Abstract: The present invention provides a tube body that is to be used in a high-temperature atmosphere and a method for stably forming a metal oxide layer on an inner surface of the tube body at a high area percentage. The tube body that is to be used in a high-temperature atmosphere according to the present invention is constituted by a heat-resistant alloy containing Cr in an amount of 15 mass % or more and Ni in an amount of 18 mass % or more, and on the inner surface, an arithmetic average roughness (Sa) of three-dimensional surface roughness satisfies 1.5?Sa?5.0 and a skewness (Ssk) of a surface height distribution satisfies |Ssk|?0.30. The heat-resistant alloy may contain Al in an amount of 2.0 mass % or more. On the inner surface, a kurtosis (Sku) of a surface height distribution of the three-dimensional surface roughness may satisfy Sku?2.5.