Provided is an apparatus that measures a thickness of a coating by selecting a wavelength of a laser based on a color of the coating using a contactless method using a photoacoustic effect and an interferometer, the apparatus including a pulsed laser source to irradiate a pulsed laser beam toward the coating, a continuous wave (CW) laser source to irradiate a CW laser beam toward the coating, a detector to detect an optical interference signal corresponding to the CW laser beam, and a signal processor to process the optical interference signal to calculate a thickness of the coating.