The invention provides a laser processing device with an economical protecting film covering method and the protecting film covering method. The protecting film covering method can inhibit the quantity of waste protecting film liquid. The laser processing device comprises a processing workbench, a laser processing component used for performing laser processing on a processed object, a storage box loading bench used for loading a storage box and a conveying component at least conveying the processed object from the storage box loaded on the storage box loading bench to the processing workbench. The laser processing device also comprises a holding workbench with a holding plane, a protecting film liquid discharging head having a slit discharging opening used for discharging protecting film liquid used for forming a protecting film and formed by water soluble resin to the surface of the processed object held on the holding workbench, a first moving component which enables the protecting film liquid discharging h
