Abstract In the current recycling system, a plastic identification is accomplished mainly by a spectrometer that recognizes a near-infrared spectrum of each plastic. This method offers higher accuracy but disadvantages in cost-efficiency, maintenance, and so on. In an attempt to develop an alternative plastic identification technology, we studied the transmittance of transparent polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS) using a laser diode. From this study, we validated the feasibility of the new plastic identification technology using the laser diode for the first time in the world. This technology can be applied to not only transparent PET, PVC, and PS, but also other transparent and colored plastics, that will bring a new solution to conventional plastic identification from the viewpoint of dimension and cost-efficiency. This paper describes our experimental study for this new technology of plastic identification using the laser diode.