A semiconductor laser device having stable heat dissipation property is provided. The semiconductor laser device includes a semiconductor laser element, a mounting body on which the semiconductor laser element is mounted, and a base body connected to the mounting body. The base body has a recess configured to engage with the mounting body and a through portion penetrating through a part of a bottom of the recess. In the specification, the remainder, which is a part of the bottom of the recess except for the through portion has a thickness equal or less than half of the largest thickness of the base body. The lowermost surface of the mounting body is spaced apart from the lowermost surface of the base body through the remainder.