PURPOSE: To continuously bore holes in a covering material at high speed by pressing the covering material composed of resin-based nonwoven fabric introduced between an embossing roll having protrusions of given shape and an ultrasonic horn having an uneven pushing face and melting parts corresponding to the projected parts of the embossing roll.

CONSTITUTION: A covering material comprising nonwoven fabric using a resin film or a resin is introduced between an embossing roll having protrusions made into the objective boring shape and an ultrasonic horn having satin like unevenness of tungsten carbide with 20-30μ thickness flame sprayed and fixed to a pushing face. The covering material is pressed against the embossing roll by the pushing face of the ultrasonic horn while being transferred at the same speed as the revolving speed of the embossing roll, parts of the covering material corresponding to the projected parts of the embossing roll are melted, the parts are caught, cut out and bored, opening edges are reinforced and enlarging of the opening parts by fray, etc., is prevented.