In the first aspect of the invention, there is provided a wristwatch case having a pipe joined and fixed thereto, the wristwatch case and the pipe having substantially no junction interface A method of fixing a pipe to a wristwatch case for obtaining this structure comprises the steps of providing a wristwatch case with a through-hole; press fitting a pipe exhibiting a through-hole/pipe press-fit overlap width (namely, outside diameter of the pipe minus diameter of the through-hole) of greater than 0 mm in the through-hole; and heating the wristwatch case after the press fitting. In the second aspect of the invention, there is provided a wristwatch case having a pipe, the wristwatch case and the pipe joined and fixed to each other through a diffusion layer. A method of fixing a pipe to a wristwatch case for obtaining this structure comprises the steps of providing a wristwatch case with a through-hole; press fitting a pipe having its surface furnished with a metallic coating, which exhibits a through-hole/pipe press-fit overlap width (namely, outside diameter of the pipe having its surface furnished with a metallic coating minus diameter of the through-hole) of not less than 0 mm, in the through-hole; and heating the wristwatch case after the press fitting in vacuum or a reducing gas.