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 a laser light converging step of converging the laser light at the object so as to form the modified region along a part corresponding to the through hole in the object; an etch resist film producing step of producing an etch resist film resistant to etching on an outer surface of the object after the laser light converging step; and an etching step of etching the object so as to advance the etching selectively along the modified region and form the through hole after the etch resist film producing step; while the laser light converging step exposes the modified region to the outer surface of the object.