To sort a mixture of conductive material pieces and plastic material pieces with higher accuracy.

The subject apparatus is provided with an opposed electrode plate 4 slanted in a direction different from a moving direction, a high voltage electric source 5 generating an electrostatic field in a sorting space 3 by applying high voltage on a belt electrode 2 and the opposite electrode plate 4, and a mixture supply device 6 supplying the mixture of aluminum pieces and PVC (polyvinyl chloride) pieces to the upstream side of the belt electrode 2. Of the supplied mixture, the aluminum pieces are made to slip and drop to the lower portion in a slanted direction by bringing the aluminum pieces into contact with the belt electrode 2 to give them the same polarity as that of the belt electrode 2 for repulsion towards the belt electrode 2, and the PVC pieces are transferred to the downstream in the moving direction by making them be attracted to the belt electrode 2 by an image force owing to polarization, thereby the PVC pieces being separated from conductive material pieces.