Provided is a semiconductor device with favorable electrical characteristics. Provided is a semiconductor device with stable electrical characteristics. Provided is a manufacturing method of a semiconductor device with a high yield. The manufacturing method includes a first step of forming an insulating film over a substrate, a second step of transferring the substrate in an atmospheric atmosphere, a third step of heating the insulating film, and a fourth step of forming a metal oxide film. The third step and the fourth step are successively performed in an atmosphere where water vapor partial pressure is lower than water vapor partial pressure in the atmospheric air.