An air dryer includes a supporting base, a drying agent container, and an outer cover. The supporting base includes an inlet for receiving compressed air to be subject to a drying process and an outlet for delivering the processed compressed air that has undergone the drying process. The drying agent container is a container supported on the supporting base, contains a drying agent in the interior, and enables the drying process to be performed by passing the compressed air from the inlet through the drying agent. The outer cover surrounds the outer side of the drying agent container on the supporting base and defines a chamber for storing the compressed air between itself and the drying agent container. The supporting base includes first and second mounting surfaces, which are oriented in different directions, and a plurality of inlets, which are oriented in different directions and receive the compressed air.