To provide a self-cleaning type positioning pulley used in a semi-plastic matter cutter using a running wire and discharging the cut refuse of the semi-plastic matter adhered to the bottom part of a positioning groove itself to be kept clean.

The extrusion space 5b of the cut refuse of the semi-plastic matter wider than the positioning groove 5a of the positioning pulley 5 is continuously provided to the bottom part of the positioning groove 5a along the circumference. The extrusion space 5b of the cut refuse of the semi-plastic matter partially communicates each with a large number of discharge ports 5c of the cut refuse of the semi-plastic matter opened to at least one of both side surfaces of the positioning pulley 5. The cut refuse 10 of the semi-plastic matter adhered to the bottom part of the positioning groove 5a is extruded to the extrusion space 5b and naturally discharged from the discharge ports 5c accompanied by the rotation of the positioning pulley 5.