A rotating shaft (23) is inserted through an axial center of a cutter wheel tip for scribing a brittle object. The rotating shaft (23) is integrally provided with the cutter wheel tip. The rotating shaft (23) is inserted into supporting holes (14) provided in side walls (11) of a tip holder (11) so as to be supported. A groove (13) is formed in an upper portion of each supporting hole (14) along an axial direction of the supporting hole (14).