A laser irradiation apparatus may include: an irradiation head section including first and second irradiation heads each configured to perform laser light irradiation on a workpiece; a laser unit section including first and second laser units configured to respectively output first laser light and second laser light; a beam delivery section provided in an optical path between the laser unit section and the irradiation head section, and configured to perform switching of optical paths between optical paths of the first laser light and the second laser light to cause the first or second laser light to enter the first or second irradiation head; a first beam property varying section provided in an optical path between the first laser unit and the irradiation head section; and a second beam property varying section provided in an optical path between the second laser unit and the irradiation head section.