Abstract: A composite plastics sheet made of a polystyrene base resin or an ABS base resin is provided. The composite plastics sheet has a conductive covering layer laminated by co-extrusion on the face of the substrate sheet. The material for the conductive covering layer is made of a polystyrene base resin or an ABS base resin and mixed with a conductive carbon black material, such as furnace black or channel black, in an amount such that the flow index at the extrusion step thereof at 200.degree. C. and under a loading of 5 kg is not lower than 0.1 g/10 min and such that the surface specific resistance of the resultant mixture is not more than 10.sup.10 ohms.