A portable wireless terminal for performing visible light communication with other devices through free space includes an optical detector for generating an electrical signal after photoelectrically converting some of optical signal input from free space and outputting the electrical signal; a reflector for retro-reflecting the others of the optical signal incident on the concave grooves, the reflector having a reflection surface on which at least one concave groove is formed; and a modulator for outputting the retro-reflected optical signal after data modulation.