By irradiating laser light 20 obliquely onto a substrate 6, the laser soldering apparatus reduces the laser light passing through an insertion hole 61a in the substrate 6 and prevents damage to low-heat-resistance portions of a component 62 disposed on the rear surface side of the substrate 6. Moreover, the substrate 6 can be observed from a normal direction with a camera 23. Therefore, even if the insertion hole 61 for inserting a component lead or the like is provided in the substrate 6, the laser light does not leak out to the side of a component mounting surface 17 of the substrate 6.