A laser module includes: a heat sink that releases heat from a member in contact with the heat sink; a sub-mount substrate that is disposed on the heat sink and made of an insulating material; a feeding layer that is disposed on the sub-mount substrate; and a laser diode array that has plural light-emitting portions disposed on the feeding layer in a parallel arrangement. A linear expansion coefficient of the sub-mount substrate is made smaller than a linear expansion coefficient of the laser diode array, and the linear expansion coefficient of the sub-mount substrate in a state connected to the heat sink having a larger linear expansion coefficient than the laser diode array is set to fall within a predetermined range including the linear expansion coefficient of the laser diode array.