The purpose of the present invention is to obtain a laser cutting device and a laser cutting method, which are capable of cutting an object to be processed with a thickness using a laser having a shorter wavelength than a CO2 laser. A laser cutting device (10), wherein a laser beam (a YAG-based laser having a shorter wavelength than a CO2 laser) for cutting an object to be processed (30) is emitted from a laser emission unit (24), and focused by an optical system (26) such that the cross-sectional shape of the laser beam becomes an elliptical shape and the long axis direction of the elliptical shape and the direction of the progress of cutting of the object to be processed (30) match, and the elliptically focused laser beam contributes to the temperature increase of a molten pool within the object to be processed (30).