A laser light source module, comprising: a plate-shaped stem; a power supply lead pin (2A, 2B) that serves as a power supply line for a semiconductor laser array, said power supply lead pin (2A, 2B) having an upper end protruding from an upper surface being one of main surfaces of said stem and a lower end penetrating to extend toward a lower surface side, the lower surface being the other of the main surface of said stem; a block fixed to the upper surface of said stem; a submount substrate that is fixed to a surface of said block and includes said semiconductor laser array mounted thereon, the surface being parallel to the upper surface of said stem; said semiconductor laser array located on said submount substrate such that a light emitting direction is parallel to the upper surface of said stem; and a collimator lens array that is located on a front surface of said semiconductor laser array and converts an output light beam of said semiconductor laser array into a parallel light beam, wherein said collimator lens array is fixed to a surface of said block, the surface being vertical to the upper surface of said stem, side surfaces of said stem have positioning notches and fixing notches, when said laser light source module is disposed on a fixing base, said positioning notches are fitted to positioning protrusions located on said fixing base to define a position of said laser light source module to be disposed on said fixing base, said positioning notches are provided in a pair at both end portions of a side surface of said stem, said side surface being located on a front side of said stem, said front side being the side of the stem where the front surface of said semiconductor laser array is located and from which light is emitted in said light emitting direction; said fixing notches are provided in a pair on side surfaces of said stem on side direction sides of said light emitting direction, and said fixing notches have a semicircular shape in a plan view. a plate-shaped stem; a power supply lead pin (2A, 2B) that serves as a power supply line for a semiconductor laser array, said power supply lead pin (2A, 2B) having an upper end protruding from an upper surface being one of main surfaces of said stem and a lower end penetrating to extend toward a lower surface side, the lower surface being the other of the main surface of said stem; a block fixed to the upper surface of said stem; a submount substrate that is fixed to a surface of said block and includes said semiconductor laser array mounted thereon, the surface being parallel to the upper surface of said stem; said semiconductor laser array located on said submount substrate such that a light emitting direction is parallel to the upper surface of said stem; and a collimator lens array that is located on a front surface of said semiconductor laser array and converts an output light beam of said semiconductor laser array into a parallel light beam, wherein said collimator lens array is fixed to a surface of said block, the surface being vertical to the upper surface of said stem, side surfaces of said stem have positioning notches and fixing notches, when said laser light source module is disposed on a fixing base, said positioning notches are fitted to positioning protrusions located on said fixing base to define a position of said laser light source module to be disposed on said fixing base, said positioning notches are provided in a pair at both end portions of a side surface of said stem, said side surface being located on a front side of said stem, said front side being the side of the stem where the front surface of said semiconductor laser array is located and from which light is emitted in said light emitting direction; said fixing notches are provided in a pair on side surfaces of said stem on side direction sides of said light emitting direction, and said fixing notches have a semicircular shape in a plan view.