A method of generating a tomographic image includes detecting an interference signal containing cross-sectional information of a target object as raw data of the target object, the raw data being phase-modulated in a first direction with respect to a cross section of the target object; demodulating the raw data by adjusting at least one parameter of a filter function defining filtering using a fixed window size; and generating a tomographic image of the target object by performing signal processing on the demodulated raw data.