Abstract: This laser processing apparatus includes an amp fiber, a seed laser oscillating unit, a fiber core exciting unit, a laser emitting unit, a controlling unit, a light sensor, etc. A Q-switched pulse seed laser beam from the seed oscillating unit enters into one end surface of the amp fiber, and a continuously oscillated core excitation light from the fiber core exciting unit 14 enters into the other end surface. The seed laser beam is amplified in the activated core during the propagation through the amp fiber and comes out as a high-power processing laser beam from the other end surface of the amp fiber. The light sensor 64 feeds back the laser power of the processing laser beam to the seed laser oscillating unit.