The semiconductor laser unit includes: a metal plate having a center portion wider than the remaining portions; a flexible substrate having a first opening; a substrate mounted on the center portion; a semiconductor laser placed on the substrate; a frame having a second opening and fixing the flexible substrate in the state of being bent along from the top surface to both side faces of the metal plate; and an optical element covering the second opening. The flexible substrate is fixed so that the first opening extends over the top surface and both side faces of the center portion.