A semiconductor light-emitting device can include high heat dissipation properties and a high degree of mounting flexibility. Also a surface light source can be configured to use the above-noted semiconductor light-emitting device. The semiconductor light-emitting element can be mounted on a package obtained by insert-molding lead frames with a resin. One of the end portions of the lead frames can be connected to respective electrodes of the semiconductor light-emitting element, and other end portions thereof can protrude outward from a resin molded portion of the package. One of the lead frames can include a block body on which the semiconductor light-emitting element is disposed. The block body protrudes from the resin molded portion. The semiconductor light-emitting device having the above structure and a circuit substrate can be mounted on a metal base which can be brought into direct contact with the block body. Alternatively, the metal base and the semiconductor light-emitting device can be disposed with a heat conducting sheet sandwiched therebetween.