A laser processing method of converging laser light into an object to be processed made of silicon so as to form a modified region and etching the object along the modified region so as to form the object with a through hole comprises an etch resist film producing step of producing an etch resist film resistant to etching on an outer surface of the object; a laser light converging step of converging the laser light at the object after the etch resist film producing step so as to form the modified region along a part corresponding to the through hole in the object and converging the laser light at the etch resist film so as to form a defect region along a part corresponding to the through hole in the etch resist film; and an etching step of etching the object after the laser light converging step so as to advance the etching selectively along the modified region and form the through hole.