In an air composition maintenance operation of this interior air-conditioning device, a controller causes a gas supply device to perform a first supply operation, a second supply operation, an outside-air supply operation and a standby operation, while switching therebetween. In the first supply operation, first low-oxygen-concentration air is supplied to an interior. In the second supply operation, second low-oxygen-concentration air having a lower oxygen concentration than the first low-oxygen-concentration air is supplied to the interior. In the outside-air supply operation, outside air is supplied to the interior. In the standby operation, the supply of outside air and low-oxygen-concentration air to the interior is stopped.
