A photoacoustic tomography apparatus comprising a light source adapted to irradiate a specimen with light at a predetermined time followed by a waiting time before a next irradiation, and comprising a received data processing apparatus of photoacoustic tomography of receiving an acoustic wave generated by irradiating the light to the specimen and constructing an image from an electrical signal obtained from the received acoustic wave, comprising: a plurality of electrical signal conversion means (1-1, 1-2,..., 1-N) that digitize received signals from a plurality of acoustic wave detectors (54-1, 54-2,..., 54-N) that receive the acoustic wave originated from a three-dimensional specimen region in processing; a plurality of first storage means (2-1, 2-2,..., 2-N) that store received digital signals digitized by the electrical signal conversion means; voxel data composition means that sequentially reads the received digital signals, originated from voxels which partition the specimen region, from the plurality of the first storage means, based on delay information of the acoustic waves assuming that the acoustic waves reach the respective acoustic wave detectors from the respective voxels, and composes voxel data, which is acoustic wave data of the respective voxels, by performing a delay-and-sum process; second storage means that stores the voxel data of the entire three-dimensional specimen region; image construction means that constructs an image of the entire three-dimensional specimen region based on the voxel data stored in the second storage means; and control means that sequentially stores the voxel data composed by the voxel data composition means in the second storage means, and reads the stored voxel data of the entire three-dimensional specimen region, and transmits the voxel data to the image construction means, wherein the photoacoustic tomography apparatus is adapted such that generation of the voxel data in said entire three-dimensional specimen region is ended before the next light irradiation starts. a plurality of electrical signal conversion means (1-1, 1-2,..., 1-N) that digitize received signals from a plurality of acoustic wave detectors (54-1, 54-2,..., 54-N) that receive the acoustic wave originated from a three-dimensional specimen region in processing; a plurality of first storage means (2-1, 2-2,..., 2-N) that store received digital signals digitized by the electrical signal conversion means; voxel data composition means that sequentially reads the received digital signals, originated from voxels which partition the specimen region, from the plurality of the first storage means, based on delay information of the acoustic waves assuming that the acoustic waves reach the respective acoustic wave detectors from the respective voxels, and composes voxel data, which is acoustic wave data of the respective voxels, by performing a delay-and-sum process; second storage means that stores the voxel data of the entire three-dimensional specimen region; image construction means that constructs an image of the entire three-dimensional specimen region based on the voxel data stored in the second storage means; and control means that sequentially stores the voxel data composed by the voxel data composition means in the second storage means, and reads the stored voxel data of the entire three-dimensional specimen region, and transmits the voxel data to the image construction means, wherein the photoacoustic tomography apparatus is adapted such that generation of the voxel data in said entire three-dimensional specimen region is ended before the next light irradiation starts.