A laser processing apparatus including a processing head and a light-focusing optical section for focusing a laser beam having a diffusion angle and enabling the laser beam having a convergent angle to be emitted from the processing head. The laser processing apparatus includes a transmissive optical member located upstream of the light-focusing optical section so as to transmit the laser beam while keeping the diffusion angle constant, or located downstream of the light-focusing optical section so as to transmit the laser beam while keeping the convergent angle constant. The transmissive optical member includes a focused-beam diameter increasing part for increasing a focused beam diameter of the laser beam transmitted through the focused-beam diameter increasing part, as compared to a focused beam diameter of the laser beam in a case where the laser beam is not transmitted through the focused-beam diameter increasing part but is focused by the light-focusing optical section.