A method of operating a wavelength swept source apparatus includes generating a single mode light, and generating a basic optical comb including light rays having identical frequency differences with adjacent light rays by modulating the generated single mode light. The method further includes generating other optical combs that include the same number of light rays as that of light rays of the optical comb that has a frequency band different from that of the basic optical comb, and is distributed in a frequency band wider than that in which the basic optical comb is distributed, by modulating the light rays of the basic optical comb. The light rays of the basic optical comb and the light rays included in the other optical combs are sequentially emitted according to frequencies of the light rays of the basic optical comb and the light rays included in the other optical combs.