A light-emitting unit 20 has a light-emitting unit board 21 made of resin provided with a lead frame 22. The light-emitting unit board 21 is also provided with an open window 21a for mounting a light-emitting device. The lead frame 22 comprises a lead terminal section 22a, an inner lead section 22c, and a light-emitting device mounting and connecting section 22b which is exposed within the open window 21a. The light-emitting devices 23a, 23b, and 23c are bonded with the light-emitting device mounting and connecting section 22b, and electrodes of the light-emitting devices and the lead frame are connected by a metal wire 24, wherein the open window 21a is sealed by transparent resin. The lead frame 22 is made of iron-containing copper to improve heat radiation performance of the light-emitting unit board. By increasing maximum current to be supplied to the light-emitting diodes, it is possible to increase illumination brightness and to attain speedup of image reading.