In this study, alignment change of liquid crystal domains induced by infrared irradiation was investigated for a plastic hexagonal columnar mesophase of a liquid crystalline triphenylene derivative. A uniform and anisotropic alignment change of domains was observed when polarized infrared light corresponding to the wavelength of the aromatic C-C stretching absorption band of triphenylene core was irradiated. The results strongly imply that the infrared irradiation is a possible technique for device fabrication by use of plastic columnar mesophase as a liquid crystalline semiconductor.