According to one embodiment, a method of manufacturing a semiconductor device includes forming a metal bump on a first surface side of a semiconductor chip, positioning the semiconductor chip so the metal bump contacts a pad of an interconnection substrate, and applying a first light from a second surface side of the semiconductor chip and melting the metal bump with the first light. After the melting, the melted metal bump is allowed to resolidify by stopping or reducing the application of the first light. The semiconductor chip is then pressed toward the interconnection substrate. A second light is then applied from the second surface side of the semiconductor chip while the semiconductor chip is being pressed toward the interconnection substrate to melt the metal bump. After the melting, the melted metal bump is allowed to resolidify by the stopping or reducing of the application of the second light.