A photoacoustic apparatus comprising: a light source (2a, 2b) adapted to irradiate an inspection target with a plurality of pulsed light; a detector adapted to detect acoustic waves generated in the inspection target due to the irradiation with the plurality of pulsed light; and to output analog detection signals corresponding to the detected acoustic waves; a light-quantity measurement unit (8a, 8b, 9a, 9b) adapted to measure a quantity of light output from the light source (2a, 2b); and a signal processor, which includes an A/D converter adapted to convert the analog detection signals into digital detection signals, and which is adapted to obtain information on an inside of the inspection target, a correction-amount determination unit (10, 10a, 10b) adapted to determine correction amounts for either the digital or analog detection signals, wherein the signal processor further includes a signal correction unit adapted to correct either the digital or analog detection signals based on a quantity of light measured by the light-quantity measurement unit (8a, 8b, 9a, 9b) so that variations in the intensities of either of the digital or analog detection signals, caused by a temporal change in the quantity of light output from the light source (2a, 2b), are suppressed, and wherein the signal correction unit is configured to correct the intensities of either the digital or analog detection signals using the correction amounts determined by the correction-amount determination unit (10, 10a, 10b), characterized in that the correction-amount determination unit (10, 10a, 10b) is configured to determine the correction amounts based on a constant reference light quantity for each pulsed light input in advance and the quantity of light measured by the light-quantity measurement unit (8a, 8b, 9a, 9b). a light source (2a, 2b) adapted to irradiate an inspection target with a plurality of pulsed light; a detector adapted to detect acoustic waves generated in the inspection target due to the irradiation with the plurality of pulsed light; and to output analog detection signals corresponding to the detected acoustic waves; a light-quantity measurement unit (8a, 8b, 9a, 9b) adapted to measure a quantity of light output from the light source (2a, 2b); and a signal processor, which includes an A/D converter adapted to convert the analog detection signals into digital detection signals, and which is adapted to obtain information on an inside of the inspection target, a correction-amount determination unit (10, 10a, 10b) adapted to determine correction amounts for either the digital or analog detection signals, wherein the signal processor further includes a signal correction unit adapted to correct either the digital or analog detection signals based on a quantity of light measured by the light-quantity measurement unit (8a, 8b, 9a, 9b) so that variations in the intensities of either of the digital or analog detection signals, caused by a temporal change in the quantity of light output from the light source (2a, 2b), are suppressed, and wherein the signal correction unit is configured to correct the intensities of either the digital or analog detection signals using the correction amounts determined by the correction-amount determination unit (10, 10a, 10b), characterized in that the correction-amount determination unit (10, 10a, 10b) is configured to determine the correction amounts based on a constant reference light quantity for each pulsed light input in advance and the quantity of light measured by the light-quantity measurement unit (8a, 8b, 9a, 9b).