To normally and stably operate an optical semiconductor element over a long period by preventing the optical axis of the element from being deviated from the optical axis of optical fiber due to the deformation of a base body and a frame body when the base body is fixed on an external electric circuit board with screws.

A package for storing the optical semiconductor element 4 is provided with an approximately square type metallic base body 1 having four screw fitting parts 1b forming through holes 1c on their centers on four corner parts, respectively, a metallic frame body 2 welded on the upper main face to surround the mount part 1a of the optical semiconductor element 4 and having an approximately square shape as a shape observed on a plane view and having a through hole 2a on its side part 2A and a cylindrical optical fiber fixing member 3 formed in the through hole 2a. As to each of the screw fitting parts 1b arranged on both the corner parts of the side part 2A, the center 1c-A of the through hole 1c is located on the inside held between the extended face of the outside face of the side part 2A and the extended face of the inside face and the base part 1b-A of a projected part is formed so as to be located on the center 2BO side of the other side part 2B adjacent to the side part 2A from the center 1c-A of the through hole 1c.