An object information acquiring apparatus has: a resonator including at least a laser medium, a flash lamp that excites the laser medium, and an output mirror that outputs laser light an oscillator that oscillates the laser light a controller that controls a timing at which the oscillator oscillates the laser light after excitation performed by the flash lamp is started a selector that selects a wavelength of the laser light a probe that detects an acoustic wave generated in an object and a processor that acquires characteristic information on the object, wherein the controller determines the timing, at which the laser light is oscillated, for each of the wavelengths in such a manner that a difference in output energy of the laser light falls within a predetermined range.
