Abstract: This application with regard to an apparatus of mixing a compressed air foam is disclosed. The disclosed application includes a first mixing unit that receives fire water and an undiluted foam solution, and adjusts an inflow of the undiluted foam solution so that a supply amount of the undiluted foam solution is adjusted in proportion to a supply amount of the fire water, and mixes the received fire water and undiluted foam solution to produce a foam aqueous solution; and a second mixing unit that mixes a compressed gas with a foam aqueous solution produced in the first mixing unit to produce a compressed air foam.