The present invention relates to a cleaning device for electrical-discharge machining fluid that cleans electrical-discharge machining fluid of an electrical-discharge machining device including a machining tank that is filled with the oil-based electrical-discharge machining fluid and in which a workpiece is machined by applying a pulse voltage between the workpiece and a machining electrode and a machining-fluid storage tank storing the electrical-discharge machining fluid to be used in the machining tank, the cleaning device including a cleaning-material storage container, which stores a cleaning material made of a granular porous material having a specific gravity equal to or higher than that of the electrical-discharge machining fluid and a grain diameter between 0.01 millimeters and 10 millimeters, in a flow channel that causes the electrical-discharge machining fluid to flow between the machining tank and the machining-fluid storage tank.