To improve the performance of a semiconductor device, a semiconductor device manufacturing method includes an exposing process of performing pattern exposure of a resist film formed on a substrate by using EUV light reflected from a front surface of an EUV mask as a reflective mask. In this exposing process, the resist film is subjected to pattern exposure by repeating a process of irradiating the resist film with the EUV light by changing a focal position of the EUV light with which the resist film is irradiated, along a film thickness direction of the resist film. After this exposing process, the resist film subjected to pattern exposure is developed to form a resist pattern.