A plastic sheet has a groove as a ruled line (21) in at least one surface of a plastic sheet wherein the groove is composed of a cut portion or a deep recess portion (22) and a shallow recess portion (23) in the longitudinal direction of the groove, and chamfered portions (24) having a radius of curvature of 0.05-1 mm are formed at both ends in the longitudinal direction of the bottom of the shallow recess portion (23). <IMAGE>
