PURPOSE: To provide a finned metal pipe of a small size and a light weight at low cost by providing spiral fins on the outer peripheral surface of the main body of a metal pipe, and forming the contour of fins into a substantially square shape when one end portion is viewed from another end portion.
CONSTITUTION: In the container of a heat pipe 1, spiral fins 4 are integrally formed on the outer peripheral surface of the main body 5 of each metal pipe of a dual tubular structure consisting of a steel inner pipe 2 and an aluminum outer pipe 3 hermetically fitted to and put over the steel inner pipe 2. The contour of each fin 4 when one end side of the main body 5 of the metal pipe is viewed from another end side thereof becomes a substantially square shape. Accordingly, only small spaces are formed between neighboring fins 4 of heat pipes 1. For example, when the finned metal pipe 1 is used in the heat pipe of the waste heat recovering device, spaces produced between fins of heat pipes become small.