A laser diode module is provided which is capable of suppressing reduction in the efficiency of laser beam coupling with an optical fiber even in the case where a warp is caused in the mounting surface of a thermo electrical cooler on which a laser diode chip is mounted. A laser diode module has a heat sink and optical coupling portion mounted directly or indirectly on a mounting surface of a thermo electrical cooler. A laser diode chip and the optical coupling portion are located on the same side of the mounting surface along the emitting direction of a laser beam emitted from the laser diode chip, with respect to a first center line (Lcpp) intersecting perpendicularly with a tangential plane tangent to the mounting surface of the thermo electrical cooler at the center thereof and/or a second center line passing through the center of the mounting surface of the thermo electrical cooler and perpendicular to both the first center line and an axis representative of the emitting direction of the laser beam.