The present disclosure discloses a flat substrate heating apparatus including a module support plate having a plurality of unit module regions placed on an upper surface thereof; a plurality of laser light source modules having a plurality of laser light source devices and seated on unit module regions of the module support plate, respectively; a power supply board placed below the module support plate and configured to supply power to the laser light source module; and an electrode terminal electrically connecting the laser light source module and the power supply board while detachably securing them to upper and lower surfaces of the module support plate.