Abstract: A new foam spraying apparatus 1 is described for a liquid container. It comprises a piston and cylinder unit (20; 37) for the air and a piston and cylinder unit (21; 38) for the liquid in which arrangement the piston and cylinder units (20, 37; 21, 38) each are provided with an inlet valve (30; 44) and with an outlet valve (24) and are co-operating being coupled to each other. Furthermore a mixing chamber (14) for the mixture of air and liquid and a spraying head (2) with a foam delivery opening (9) are provided. The cylinder (20) of the first unit and the piston (21) of the second unit are interconnected to an intermediate part (5). Furthermore the piston (37) of the first unit and the cylinder (38) of the second unit are also interconnected to a base part (4) in such a manner that the intermediate part (5) and the base part (4) mesh and are movable relative to each other.