To irradiate a subject with pulsed laser beams having greater temporal variation of light intensity than the temporal variation of light intensity of pulsed laser beams emitted from a laser source in a photoacoustic image generating apparatus.

A laser unit 13 emits pulsed laser beams. A waveform shaping means 14 shapes the waveform of the pulsed laser beam made incident from the laser unit 13 so that the temporal variation of the light intensity may be increased. The subject is irradiated with the waveform-shaped pulsed laser beam light, and after the irradiation, photoacoustic signals generated inside the subject are detected using a probe 11. Using a photoacoustic image reconstructing means 24, a detection/logarithmic transformation means 25, and a photoacoustic image constructing means, photoacoustic images are generated from the detected photoacoustic signals.