A kneading device uniformly kneads materials to be kneaded while efficiently and quickly kneading the materials to be kneaded. A kneading device includes a kneading chamber accommodating materials to be kneaded and a pair of rotors (10) . The pair of rotors (10) is rotated in the kneading chamber and kneads the materials to be kneaded by a plurality of kneading blades (20). The plurality of kneading blades (20) in each rotor (10) is composed only of inclined blades inclined to the same direction in a rotational direction (R) of the rotor (10) with respect to an axial direction (X) of the rotor (10) when the rotor (10) is developed into a planar state. The rotor (10) has bent blades (30, 40) which are bent at bent portions (31, 41) to change tilt angles (E, F) with respect to the axial direction (X) of the rotor (10) in the plurality of kneading blades (20).