The manufacturing method of a semiconductor device can improve the mechanical strength of a pad more than before, and suppress the occurrence of a crack. The manufacturing method of a semiconductor device includes: forming a first pad constituted by a first metal layer; forming an insulating layer on the first pad; providing an opening portion in the insulating layer by removing the insulating layer on at least a partial region of the first pad; forming a second pad constituted by a second metal layer in the opening portion of the insulating layer so as to have a film thickness that is smaller than the film thickness of the insulating layer; and forming a third pad constituted by a third metal layer on the second pad.