A kneading tank inversion discharging sealed pressurized type kneading machine enables one to solve a problem of time and effort required for the discharge operation of the kneaded product, suppress scattering of a compounded powder compound agent, and recover almost the entire amount of the compound agent jetted from the kneading tank for each batch. A kneading machine is provided with a kneading rotor (10), wherein a kneading tank (3), a stocking opening (4) of which can be closed by an openable pressure lid (5), can be inversed for discharging a kneaded product, and wherein a front wall (8a) of an opening wall (8) which surrounds the four peripheries of the stocking opening is attached so as to be suspended downward from the kneading tank by a hinge (26) when the tank is inverted. The kneading tank can be inverted within the range of 90 to 120 DEG. An inner pressure cover (45) which covers the pressure lid (5) and the stocking opening (4) is provided, a duct (53) of a collecting device (50) is connected to the inner pressure cover to collect the jetted powder compound agent within the inner pressure cover, and the powder compound agent collected by a filter (51) of the collection device can be recovered in the kneading tank (3).