A semiconductor laser device includes a semiconductor laser element, a sub mount member, a mount section having an upper surface on which the semiconductor laser element is mounted with the sub mount member interposed therebetween, a lead pin disposed at left and right sides of the mount section, a retainer that retains the mount section and the lead pin together and that is composed of an insulative material, and a protrusion protruding toward the left and right sides of the mount section. A lower surface of the mount section is parallel to an upper surface of the mount section and protrudes from a lower surface of the retainer.