An optical transmitting unit transmits a pulsed laser beam oscillated by a pulsed laser beam oscillator to a focusing unit in a laser processing apparatus. A wavelength band expanding unit expands the wavelength band of the pulsed laser beam, and a pulse width expanding unit increases the pulse width of the expanded pulsed laser beam. A focusing lens focuses the expanded pulsed laser beam. An optical fiber transmits the focused pulsed laser beam through a collimating lens and a pulse width compressing unit compresses the pulse width of the collimated pulsed laser beam to restore the original pulse width for transmission.