A mount member, on an upper surface of which a first semiconductor laser element and a second semiconductor laser element are to be mounted, the mount member comprising: a first conduction part including a first mounting region on which the first semiconductor laser element is to be mounted, and a first wiring region to which a wiring electrically connected to the first semiconductor laser element is to be bonded; and a second conduction part arranged adjacent to the first conduction part and including a second mounting region on which the second semiconductor laser element is to be mounted, and a second wiring region to which a wiring electrically connected to the second semiconductor laser element is to be bonded, wherein an upper surface of the mount member has a quadrangular shape, wherein the direction of the short side of the quadrangular shape is defined as a first direction, and the direction of the long side of the quadrangular shape is defined as a second direction; wherein the first conduction part is smaller in length in the first direction, which is parallel to a light emission end surface of the first semiconductor laser element as seen in a top view when the first semiconductor laser element is mounted on the first mounting region, than in the second direction perpendicular to the light emission end surface, in relation to the second direction, the first wiring region extends further than the first mounting region, in a direction from the light emission end surface of the first semiconductor laser element to an end surface of the first semiconductor laser element opposite to the light emission end surface, in relation to the second direction, the second conduction part extends further than the first conduction part in a direction from a light emission end surface of the second semiconductor laser element to an end surface of the second semiconductor laser element opposite to the light emission end surface when the second semiconductor laser element is mounted on the second mounting region, and the second conduction part extends toward the first conduction part in the first direction from a region where the second conduction part extends further than the first conduction part, and the first mounting region, the first wiring region, and the second wiring region are arranged on a phantom line running along the second direction and passing through a center of the light emission end surface of the first semiconductor laser element as seen in the top view with the first wiring region being arranged between the first mounting region and the second wiring region. a first conduction part including a first mounting region on which the first semiconductor laser element is to be mounted, and a first wiring region to which a wiring electrically connected to the first semiconductor laser element is to be bonded; and a second conduction part arranged adjacent to the first conduction part and including a second mounting region on which the second semiconductor laser element is to be mounted, and a second wiring region to which a wiring electrically connected to the second semiconductor laser element is to be bonded, wherein an upper surface of the mount member has a quadrangular shape, wherein the direction of the short side of the quadrangular shape is defined as a first direction, and the direction of the long side of the quadrangular shape is defined as a second direction; wherein the first conduction part is smaller in length in the first direction, which is parallel to a light emission end surface of the first semiconductor laser element as seen in a top view when the first semiconductor laser element is mounted on the first mounting region, than in the second direction perpendicular to the light emission end surface, in relation to the second direction, the first wiring region extends further than the first mounting region, in a direction from the light emission end surface of the first semiconductor laser element to an end surface of the first semiconductor laser element opposite to the light emission end surface, in relation to the second direction, the second conduction part extends further than the first conduction part in a direction from a light emission end surface of the second semiconductor laser element to an end surface of the second semiconductor laser element opposite to the light emission end surface when the second semiconductor laser element is mounted on the second mounting region, and the second conduction part extends toward the first conduction part in the first direction from a region where the second conduction part extends further than the first conduction part, and the first mounting region, the first wiring region, and the second wiring region are arranged on a phantom line running along the second direction and passing through a center of the light emission end surface of the first semiconductor laser element as seen in the top view with the first wiring region being arranged between the first mounting region and the second wiring region.