A laser oscillation apparatus which generates pulse light with an optical resonator and a plurality of fiber amplifiers arranged at a circulation optical path, comprising: a laser light source which generates laser light for excitation; a first fiber amplifier which includes a mode-locking type amplitude modulator to operate light with a desired frequency to be grown as being an integral multiple of a frequency corresponding to an optical path length of the circulation optical path and which emits pulse laser light with the desired frequency while the laser light generated by the laser light source is entered; an optical resonator which resonates and accumulates the pulse laser light emitted from the first fiber amplifier; a second fiber amplifier which includes an adjustment cable corresponding to a wavelength of the pulse laser light and which amplifies the pulse laser light emitted from the optical resonator; a first photodiode which extracts a part of the laser light from the first fiber amplifier; a splitter which divides an output signal of the first photodiode into two; a first RF amplifier which amplifies one of the two output signals from the splitter; a band-pass filter which extracts an RF signal of the laser light with the desired frequency among output signals of the first RF amplifier; a phase modulator which performs phase modulation of the RF signal passing through the band-pass filter; a second RF amplifier which drives the amplitude modulator with the phase-modulated RF signal; and a second photodiode which monitors the other of the two output signals from the splitter, wherein the pulse laser light is self-oscillation-amplified and accumulated in the optical resonator as circling on the circulation optical path which is structured with the first fiber amplifier, the optical resonator and the second fiber amplifier, and the adjustment cable on the circulation optical path is a cable which finely adjusts the optical path length of the circulation optical path. a laser light source which generates laser light for excitation; a first fiber amplifier which includes a mode-locking type amplitude modulator to operate light with a desired frequency to be grown as being an integral multiple of a frequency corresponding to an optical path length of the circulation optical path and which emits pulse laser light with the desired frequency while the laser light generated by the laser light source is entered; an optical resonator which resonates and accumulates the pulse laser light emitted from the first fiber amplifier; a second fiber amplifier which includes an adjustment cable corresponding to a wavelength of the pulse laser light and which amplifies the pulse laser light emitted from the optical resonator; a first photodiode which extracts a part of the laser light from the first fiber amplifier; a splitter which divides an output signal of the first photodiode into two; a first RF amplifier which amplifies one of the two output signals from the splitter; a band-pass filter which extracts an RF signal of the laser light with the desired frequency among output signals of the first RF amplifier; a phase modulator which performs phase modulation of the RF signal passing through the band-pass filter; a second RF amplifier which drives the amplitude modulator with the phase-modulated RF signal; and a second photodiode which monitors the other of the two output signals from the splitter, wherein the pulse laser light is self-oscillation-amplified and accumulated in the optical resonator as circling on the circulation optical path which is structured with the first fiber amplifier, the optical resonator and the second fiber amplifier, and the adjustment cable on the circulation optical path is a cable which finely adjusts the optical path length of the circulation optical path.