A laser processing apparatus including a processing head for applying a laser beam to a workpiece. The processing head includes a focusing lens and a collecting unit provided between the focusing lens and the workpiece for collecting debris generated by the application of the laser beam focused by the focusing lens to the workpiece. The collecting unit includes a suction source for sucking the debris and a suction line having one end connected to the suction source and the other end opening to the front side of the workpiece. The laser processing apparatus further includes a cleaning liquid supplying unit for supplying a cleaning liquid to the suction line.