A manufacturing method of a semiconductor device includes mounting a semiconductor element on a first electrode disposed on a first surface of a substrate; preparing a metal plate including a main body part and a projection part; mounting the metal plate on the first surface side of the substrate, by joining the projection part to a second electrode that is disposed on the first surface of the substrate; sealing the semiconductor element and the projection part with a sealing resin; and forming an electrode terminal made of a base end part that is connected to the second electrode and has a side surface that is covered by the sealing resin, and a tip end part that is integrally formed with the base end part and that projects from a front surface of the sealing resin, by etching the main body part excluding a portion overlapping with the projection part.