A hologram observation method capable of accurately estimating a three-dimensional wave source distribution even when a wave source is close to a hologram observation plane. The hologram observation is performed according to a two-frequency hologram observation method to reconstruct a hologram image. A three-dimensional wave source position is obtained from the reconstructed hologram image, a virtual unit wave source is disposed at the obtained wave source position and an observed wave is synthesized. A hologram image obtained from the synthesized observed wave is reconstructed, and a wave source intensity obtained from the measured hologram image is divided by a wave source intensity at the hologram image obtained from the synthesized observed wave, thereby obtaining a true complex amplitude of the wave source. An area having an intensity more than a predetermined value in the hologram image which is obtained from the synthesized observation wave is excluded from a search range, and each of the foregoing steps is executed.