Abstract: An apparatus for photosynthesis includes a unique arrangement for supplying light and CO.sub.2 -containing air to a reaction chamber in a sure and stable manner. The reaction chamber is irradiated for photosynthesis from the inside and/or outside thereof in an intermittent mode. CO.sub.2 -containing air is routed from a CO.sub.2 source to a rotatable disc which is positioned in a bottom portion of the apparatus. Part of the CO.sub.2 -containing air is ejected sideways from the disc to cause it into rotation, while the rest of the air is ejected upwardly into the reaction chamber. The reaction chamber is partitioned into a plurality of compartments which are sequentially supplied with the CO.sub.2 -containing air in accordance with the rotation of the disc.