Method and device for excavating submerged stratum

An excavation technique for a stratum capable of excavating a submerged stratum such as a layer containing an underground resource by using laser irradiation in liquid is provided. In this technique, a laser beam transmitted through laser transmission means is irradiated in liquid in form of a laser beam having a wavelength with high absorptance of the liquid by laser-induced bubble generation means , generating a bubble flow , thus excavation of a submerged stratum may be carried out by using a laser-induced destruction effect. Moreover, a laser beam having low absorptance of the liquid is irradiated by laser irradiation means and passed through the bubble flow , thereby applying a thermal effect to a stratum to destroy rock and excavate the stratum. The destruction effect and the thermal effect also may be cooperatively worked.