An air purifying system includes: a carbon dioxide remover including first and second spaces partitioned by a gas permeable membrane with 50 nm or less diameter micropores; a feed passage leading to-be-purified air from a room to the first space; a supply passage supplying clean gas having lower carbon dioxide and higher oxygen concentrations than the to-be-purified air to the second space; a discharge passage discharging, from the second space, mixed gas; a return passage leading purified air from the first space into the room, the purified air resulting from removing carbon dioxide from the to-be-purified air; and adjusting equipment adjusting a gas pressure in the first and second spaces to be substantially equal to each other. The to-be-purified air flows in the first space along a surface of the gas permeable membrane, and the clean gas flows in the second space along a surface of the gas permeable membrane.