To improve the kneading process of a continuous mixer by kneading the forcibly reverse-sent part of a mixed material while it is mutually com pressed and sheared when a variety of powder and granule are continuously kneaded by a mixing tank.

A rotary shaft 4 is equipped with screw blades 7, mixing blades 9 and reverse-sending blades 10 and is rotatable centered around the central line of the rotary shaft 4. A mixed material 1 to be supplied continuously is mixed while it is diffusively convected by the rotation of the screw blades 7 and at the same time, is continuously conveyed toward the mixing blades 9 and the reverse-sending blades 10. The conveyed mixed material 1 is sheared by the rotation of the mixing blades 9 and at the same time, is conveyed toward a discharge gate 8. However, part of the conveyed mixed material 1 is returned by the reverse-sending blades 10. The part, which is returned by the reverse- sending blades 10, of the mixed material 1 collides with the mixed material 1 to be continuously sent later by the mixing blades 1 and consequently is compressed to be squeezed out of a space between the blades. Thus the kneading of the mixed material 1 is performed.