To stably segmentize mother glass for substrates when a liquid crystal display panel is manufactured.

While the mother glass 11 for CF (color filter) substrates is irradiated with a laser beam oscillated from a laser oscillator 21, vicinities of the laser beam irradiation region are cooled by making cooling water impinge on them from a cooling nozzle 22. Thereby scribe lines SL are formed. Subsequently the mother glass 11 for the CF substrates is segmentized along the scribe lines SL formed thereon so as to form a plurality of the CF substrates. Similarly, by forming scribe lines on the mother glass for TFT substrates and segmentizing it, a plurality of the TFT substrates are formed. Then the formed CF substrate and the formed TFT substrate are stuck to each other.