An apparatus for processing a holographic image, the apparatus comprising: a first calculator configured to calculate, by performing a first calculation that relates to each of an image for a left eye and an image for a right eye that are included in input image data: values of a light waveform for a left pupil, indicating a waveform which light incident to the left eye has on a left pupil surface such that the left eye recognizes the image for the left eye; and values of a light waveform for a right pupil, indicating a waveform which light incident to the right eye has on a right pupil surface such that the right eye recognizes the image for the right eye; a storage configured to store the calculated values of the light waveform for the left pupil at a first memory address and to store the calculated values of the light waveform for the right pupil at a second memory address; a second calculator configured to calculate values of a waveform of light to be modulated by a spatial light modulator by performing a second calculation that uses the calculation results stored at the first and second memory addresses such that an image window of the image for the left eye is spatially separated from an image window of the image for the right eye within a viewing window; and a scaler configured to, before the first calculator performs the first calculation, change the resolution of the image for the left eye, to be less than or equal to a resolution representable in the image window of the image for the left eye, and the resolution of the image for the right eye, to be less than or equal to a resolution representable in the image window of the image for the right eye; and wherein the apparatus further comprises a pupil measurer configured to measure a size of at least one from among the left pupil and the right pupil, wherein each of the size of the image window of the image for the left eye and the size of the image window of the image for the right eye is smaller than or equal to the measured size of the at least one pupil. a first calculator configured to calculate, by performing a first calculation that relates to each of an image for a left eye and an image for a right eye that are included in input image data: values of a light waveform for a left pupil, indicating a waveform which light incident to the left eye has on a left pupil surface such that the left eye recognizes the image for the left eye; and values of a light waveform for a right pupil, indicating a waveform which light incident to the right eye has on a right pupil surface such that the right eye recognizes the image for the right eye; values of a light waveform for a left pupil, indicating a waveform which light incident to the left eye has on a left pupil surface such that the left eye recognizes the image for the left eye; and values of a light waveform for a right pupil, indicating a waveform which light incident to the right eye has on a right pupil surface such that the right eye recognizes the image for the right eye; a storage configured to store the calculated values of the light waveform for the left pupil at a first memory address and to store the calculated values of the light waveform for the right pupil at a second memory address; a second calculator configured to calculate values of a waveform of light to be modulated by a spatial light modulator by performing a second calculation that uses the calculation results stored at the first and second memory addresses such that an image window of the image for the left eye is spatially separated from an image window of the image for the right eye within a viewing window; and a scaler configured to, before the first calculator performs the first calculation, change the resolution of the image for the left eye, to be less than or equal to a resolution representable in the image window of the image for the left eye, and the resolution of the image for the right eye, to be less than or equal to a resolution representable in the image window of the image for the right eye; and wherein the apparatus further comprises a pupil measurer configured to measure a size of at least one from among the left pupil and the right pupil, wherein each of the size of the image window of the image for the left eye and the size of the image window of the image for the right eye is smaller than or equal to the measured size of the at least one pupil.