A subject information acquiring apparatus comprising: a probe which has a plurality of elements arranged at least in a first direction, each of the plurality of elements is adapted to receive elastic waves propagating within a subject and convert the received elastic waves to received signals; a stage adapted to move the probe in a second direction; a first signal processing unit (10, 410) adapted to calculate, for each of a plurality of target positions different from each other, a first output signal corresponding to the elastic waves from the respective target position by using the received signals output by the elements, wherein each of the first output signals includes phase information regarding the elastic waves from the respective target position; a second signal processing unit (20, 420) adapted to calculate, for each of the target positions, a second output signal corresponding to the elastic waves from the respective target position by using a respective subset of the first output signals calculated for target positions which are different from each other in the second direction; and an image processing unit adapted to use the second output signals to generate image data for display, wherein at least one of the first signal processing unit (10, 410) and the second signal processing unit (20, 420) is adapted to perform adaptive signal processing to calculate the first output signal and the second output signal, respectively, wherein the second signal processing unit is further adapted to start calculating the second output signal of one of the target positions when the respective subset of the first output signals has been calculated and the respective subset for another one of the target positions has not yet been calculated. a probe which has a plurality of elements arranged at least in a first direction, each of the plurality of elements is adapted to receive elastic waves propagating within a subject and convert the received elastic waves to received signals; a stage adapted to move the probe in a second direction; a first signal processing unit (10, 410) adapted to calculate, for each of a plurality of target positions different from each other, a first output signal corresponding to the elastic waves from the respective target position by using the received signals output by the elements, wherein each of the first output signals includes phase information regarding the elastic waves from the respective target position; a second signal processing unit (20, 420) adapted to calculate, for each of the target positions, a second output signal corresponding to the elastic waves from the respective target position by using a respective subset of the first output signals calculated for target positions which are different from each other in the second direction; and an image processing unit adapted to use the second output signals to generate image data for display, wherein at least one of the first signal processing unit (10, 410) and the second signal processing unit (20, 420) is adapted to perform adaptive signal processing to calculate the first output signal and the second output signal, respectively, wherein the second signal processing unit is further adapted to start calculating the second output signal of one of the target positions when the respective subset of the first output signals has been calculated and the respective subset for another one of the target positions has not yet been calculated.