Machine for emptying, washing and sanitizing of the portable tanks used in the toilets of recreational vehicles (for example, campers, motor homes, caravans and boats), characterized by a structure widi sliding door, in which the tank is inserted; the machine comprises sensors capable of detecting the type of the tank inserted. The washing procedure starts by rotating the pour-out spout, unscrewing the lid and lifting the tank into a vertical position, thus emptying it into the drainage system. A coupling mask then automatically slides open the lid and opens all the valves and sealing plugs. A lance then injects water and detergent at high pressure inside the tank, thus washing inside. The machine then washes the outside of the tank and of the cap of the same, filling it widi sanitizing liquids, drying and re-delivering it to the user through its completely automated, electronically-controlled method thus guaranteeing hygiene and safety. The machine provides for direct connection to the sewerage system or to a collecting tank and backup systems for electricity and water supplies.