A photoacoustic apparatus comprising: an irradiation unit (110, 120) configured to irradiate a target object with light; a probe including a plurality of transducers and configured to receive acoustic waves generated from the target object irradiated with the light and to output a reception signal group; a storage unit configured to store the reception signal group output from the plurality of transducers; and a processing unit configured to determine target-object information in a region of interest of the target object, wherein the irradiation unit is configured to irradiate the target object with the light at a different position at each of a plurality of timings, wherein the probe is configured to receive, for each of the plurality of timings an acoustic wave generated by irradiated the target object with the light, and to output a plurality of reception signal groups respectively corresponding to the plurality of timings, wherein the storage unit is configured to store the plurality of reception signal groups, and wherein the processing unit is further configured to determine for each of the plurality of timings, a light fluence in the region of interest, obtain, for each of the plurality of timings, reception signals corresponding to the acoustic wave generated from the region of interest and received by the plurality of transducers, from the plurality of reception signal groups stored in the storage unit, weight, for each of the plurality of timings, the reception signals corresponding to the acoustic wave generated from the region of interest and received by the plurality of transducers with a weighting factor, and determine the target-object information in the region of interest based on the plurality of weighted reception signals respectively corresponding to the plurality of timings; and characterized in that the processing unit is configured to determine, for each of the plurality of timings, the weighting factor based on the light fluence in the region of interest. an irradiation unit (110, 120) configured to irradiate a target object with light; a probe including a plurality of transducers and configured to receive acoustic waves generated from the target object irradiated with the light and to output a reception signal group; a storage unit configured to store the reception signal group output from the plurality of transducers; and a processing unit configured to determine target-object information in a region of interest of the target object, wherein the irradiation unit is configured to irradiate the target object with the light at a different position at each of a plurality of timings, wherein the probe is configured to receive, for each of the plurality of timings an acoustic wave generated by irradiated the target object with the light, and to output a plurality of reception signal groups respectively corresponding to the plurality of timings, wherein the storage unit is configured to store the plurality of reception signal groups, and wherein the processing unit is further configured to determine for each of the plurality of timings, a light fluence in the region of interest, obtain, for each of the plurality of timings, reception signals corresponding to the acoustic wave generated from the region of interest and received by the plurality of transducers, from the plurality of reception signal groups stored in the storage unit, weight, for each of the plurality of timings, the reception signals corresponding to the acoustic wave generated from the region of interest and received by the plurality of transducers with a weighting factor, and determine the target-object information in the region of interest based on the plurality of weighted reception signals respectively corresponding to the plurality of timings; and characterized in that the processing unit is configured to determine, for each of the plurality of timings, the weighting factor based on the light fluence in the region of interest.