PROBLEM TO BE SOLVED: To prevent an excess stress from being applied to a connection part of two semiconductor chips in a semiconductor device in which a chip laminate including a small-diameter semiconductor chip and a large-diameter semiconductor chip is mounted on a top face of a base material.SOLUTION: In a semiconductor device manufacturing method, by mounting a large-diameter first semiconductor chip on a support substrate and subsequently mounting a small-diameter second semiconductor chip on the first semiconductor chip, since a tilt and slip of the second semiconductor chip mounted on the first semiconductor chip can be inhibited, an excess stress can be inhibited from being applied to a connection part of the first semiconductor chip and the second semiconductor chip.