Abstract: Provided are an electrode catalyst production system and production method omitting transferring an electrode catalyst precursor, and shortening a drying time thereof. The system has an electrode catalyst precursor production device, a washing device and a drying device. The drying device includes executors for executing: an introduction step for introducing an electrode catalyst precursor into a container main body; a drying processing step for drying the precursor by heating and depressurizing the container main body, and stirring and mixing the precursor with a stirring blade; a cooling step for cooling the precursor by cooling and depressurizing the container main body, and stirring and mixing the precursor with the stirring blade; a slow oxidation step for performing a slow oxidation treatment on the precursor by supplying air to the container main body; and a retrieving step for retrieving the precursor inside the container main body.