An apparatus for preparing food comprises a food preparation chamber with an air-permeable bottom wall and an upper air discharge opening, a fan for moving hot air successively through the bottom wall, the food preparation chamber and the discharge opening, an air channel for returning the air from the discharge opening towards the bottom wall separate from the food preparation chamber, a heat radiator positioned in the upper part of the food preparation chamber and an air guide below the food preparation chamber and on top of a bottom part for directing the air flow essentially upwards into food present in the food preparation chamber. Said air guide comprises at least one air guide rib arranged along a curved line extending substantially towards a central region of said bottom part, wherein said air guide rib is provided with a concave side which, as seen in a vertical section through said air guide rib, along at least part of its extension along said curved line includes an angle with the bottom part smaller than 90°.