A lamp includes a substrate, a heat-dissipation member, an optical member, and a heat-transfer member. The optical member, the substrate and the heat-dissipation member are arranged in this order. In two members of the heat-dissipation member and the optical member or two members of the heat-dissipation member and the substrate, one end sides thereof are fixed to each other by a fixing mechanism, and the other end sides thereof are hooked and fixed such that the two members are prevented from being displaced in a direction away from each other with the heat-transfer member located between the one end side and the other end side being a support point and the one end side being a force point.