A circuit board for supporting a semiconductor light-emitting device provided with at least a semiconductor light-emitting element and a phosphor, wherein, on the circuit board, at least a semiconductor light-emitting device including a plurality of semiconductor light-emitting elements each having a different path of a drive current to be supplied or a plurality of semiconductor light-emitting devices each having a different path of a drive current to be supplied to each semiconductor light-emitting element is mounted, the circuit board comprises a base material portion formed using a heat-conducting material;
- and a power supply conductor layer for supplying the drive currents for semiconductor light-emitting elements to the semiconductor light-emitting devices, the power supply conductor layer is formed planarly using the heat-conducting material so as to cover a planar surface of the base material portion, and the planar region of the power supply conductor layer is planarly divided by an insulator for each drive current path.