A photoacoustic image generation apparatus comprising: a laser source unit configured to sequentially emit a plurality of pulse laser beams in a predetermined wavelength sequence having at least two different wavelengths, the laser source unit including a laser rod, an excitation light source configured to irradiate the laser rod with excitation light, an optical resonator that has a pair of mirrors (53, 54) facing each other with the laser rod interposed therebetween, a Q switch which is inserted into the optical resonator, and a birefringent filter which is inserted into the optical resonator and is configured to change an oscillation wavelength of the optical resonator in association with rotational displacement of the birefringent filter; and an acoustic wave unit configured to generate a photoacoustic image, the acoustic wave unit including detection means configured to detect a photoacoustic signal generated within an object when the object is irradiated with the pulse laser beam having each wavelength included in the predetermined wavelength sequence and to generate pieces of photoacoustic data corresponding to the respective wavelengths, intensity ratio extraction means configured to extract a magnitude relation between relative signal intensities of the pieces of photoacoustic data corresponding to the respective wavelengths, photoacoustic image construction means configured to generate the photoacoustic image on the basis of the extracted magnitude relation, and a trigger control circuit configured to cause the laser rod to be irradiated with excitation light from the excitation light source while rotating the birefringent filter at a predetermined rotation speed depending on the number of wavelengths included in the wavelength sequence, and after the irradiation with the excitation light, to turn on the Q switch at a timing when a rotational displacement position of the birefringent filter is set to a position corresponding to the wavelength of the pulse laser beam to be emitted to cause the pulse laser beam to be emitted, wherein the trigger control circuit is configured to continuously rotate the birefringent filter in a predetermined direction at the predetermined rotation speed. a laser source unit configured to sequentially emit a plurality of pulse laser beams in a predetermined wavelength sequence having at least two different wavelengths, the laser source unit including a laser rod, an excitation light source configured to irradiate the laser rod with excitation light, an optical resonator that has a pair of mirrors (53, 54) facing each other with the laser rod interposed therebetween, a Q switch which is inserted into the optical resonator, and a birefringent filter which is inserted into the optical resonator and is configured to change an oscillation wavelength of the optical resonator in association with rotational displacement of the birefringent filter; and an acoustic wave unit configured to generate a photoacoustic image, the acoustic wave unit including detection means configured to detect a photoacoustic signal generated within an object when the object is irradiated with the pulse laser beam having each wavelength included in the predetermined wavelength sequence and to generate pieces of photoacoustic data corresponding to the respective wavelengths, intensity ratio extraction means configured to extract a magnitude relation between relative signal intensities of the pieces of photoacoustic data corresponding to the respective wavelengths, photoacoustic image construction means configured to generate the photoacoustic image on the basis of the extracted magnitude relation, and a trigger control circuit configured to cause the laser rod to be irradiated with excitation light from the excitation light source while rotating the birefringent filter at a predetermined rotation speed depending on the number of wavelengths included in the wavelength sequence, and after the irradiation with the excitation light, to turn on the Q switch at a timing when a rotational displacement position of the birefringent filter is set to a position corresponding to the wavelength of the pulse laser beam to be emitted to cause the pulse laser beam to be emitted, wherein the trigger control circuit is configured to continuously rotate the birefringent filter in a predetermined direction at the predetermined rotation speed.