A laser ultrasonic flaw detection apparatus in which a first laser beam is focused onto a surface of an inspection object; a second laser beam is focused onto the surface of the inspection object to detect reflected waves reflected at the surface of the inspection object, thereby acquiring a vibration displacement at the surface of the inspection object excited by ultrasonic waves generated by the first laser beam; and the presence/absence of a defect inside the inspection object, which is reflected in the vibration displacement, is detected; the laser ultrasonic flaw detection apparatus wherein the apparatus comprises: a laser light source that emits a laser beam having a single wavelength; a wavelength shifter that converts the laser beam emitted from the laser light source into a laser beam that includes at least two wavelengths; a beam splitter that demultiplexes the laser beam converted by the wavelength shifter into a laser beam having a first wavelength (λ 1) and a laser beam having a second wavelength (λ 2) which is different from the first wavelength (λ 1); a first controller that adjusts output power and pulse width of the laser beam having the first wavelength (λ 1) passed through the beam splitter; a second controller that adjusts output power and pulse width of the laser beam having the second wavelength (λ 2) passed through the beam splitter; a multiplexer that multiplexes the laser beam having the first wavelength (λ 1), which has been adjusted by the first controller, and the laser beam having the second wavelength (λ 2), which has been adjusted by the second controller, and that passes a single laser beam including the laser beam having the first wavelength (λ 1) and the laser beam having the second wavelength (λ 2); and an optical projection unit that projects the single laser beam obtained at the multiplexer to the surface of the inspection object, wherein the laser beam having the first wavelength (λ 1) is used as the first laser beam and the laser beam having the second wavelength (λ 2) is used as the second laser beam. a laser light source that emits a laser beam having a single wavelength; a wavelength shifter that converts the laser beam emitted from the laser light source into a laser beam that includes at least two wavelengths; a beam splitter that demultiplexes the laser beam converted by the wavelength shifter into a laser beam having a first wavelength (λ 1) and a laser beam having a second wavelength (λ 2) which is different from the first wavelength (λ 1); a first controller that adjusts output power and pulse width of the laser beam having the first wavelength (λ 1) passed through the beam splitter; a second controller that adjusts output power and pulse width of the laser beam having the second wavelength (λ 2) passed through the beam splitter; a multiplexer that multiplexes the laser beam having the first wavelength (λ 1), which has been adjusted by the first controller, and the laser beam having the second wavelength (λ 2), which has been adjusted by the second controller, and that passes a single laser beam including the laser beam having the first wavelength (λ 1) and the laser beam having the second wavelength (λ 2); and an optical projection unit that projects the single laser beam obtained at the multiplexer to the surface of the inspection object, wherein the laser beam having the first wavelength (λ 1) is used as the first laser beam and the laser beam having the second wavelength (λ 2) is used as the second laser beam.