The present disclosure provides a gas purge device and a gas purge method for purging a wafer container to clean wafers. The gas purge device includes a first nozzle and a gas gate. The first nozzle is coupled to a front-opening unified pod (FOUP) through a first port of the FOUP. The gas gate is coupled to the first nozzle via a first pipe. The gas gate includes a first mass flow controller (MFC), a second MFC, and a first switch unit. The first MFC is configured to control a first flow of a first gas. The second MFC is configured to control a second flow of a second gas. The first switch unit is coupled to the first MFC and the second MFC, and is configured to provide the first gas to the first nozzle through the first pipe or receive the second gas from the first nozzle through the first pipe according to a process configuration.