<p>A mixing discharge device including: a mixing chamber (1) where liquids containing a raw material, at least one of which further contains a blowing agent, are mixed under pressure; a tapered path (3) communicating with the chamber and having an inner peripheral surface where the cross section decreases in a downstream direction; a tapered piston (2) inserted into the path and having an outer peripheral surface corresponding to the inner peripheral surface; an actuator retracting the piston from a position where the inner and outer peripheral surfaces are in contact with each other to form a specific gap; a buffer path (5) communicating with the tapered path; and a discharge port (4) for ultimately discharging the mixture. The buffer path has a configuration alleviating expansion of the mixture. The actuator controls the retraction amount of the piston to vary the width D of the gap and thereby adjusts the pressure that the chamber maintains and the degree to which the pressure of the mixture is reduced in the tapered path.</p>
