An air cleaner includes a first air cleaner having an output part, a second air cleaner configured to be electrically connectable to the first air cleaner, a power adapter detachably provided to supply power to the second air cleaner, a first input terminal provided in the second air cleaner and configured to be electrically connected to the output part, a second input terminal provided in the second air cleaner and configured to be electrically connected to the power adapter; and a switch configured to electrically connect the first input terminal to the output part or to electrically connect the second input terminal to the power adapter.