PURPOSE: To prevent an ink from being accumulated at the end part of a roller by forming a plurality of pockets which force the ink from both end parts of one of a first and a second roller to the center part of said one roller by a fluid pressure in a nip part when the rollers are rotated.

CONSTITUTION: Helical inserts 36, 38 are deformed to a larger degree than a hard rubber part 34 in a nip part 46 between rollers 22, 26 by a fluid pressure in the nip part 46. Consequently, pockets 48, 50, for example, are formed in the helical inserts 36, 38. The pockets 48, 50 are formed at an interval in the axial direction along the nip part 46, instantaneously when an ink kneading roller 22 is rotated in the direction of 52 and an intermediate roller 26 is rotated in the direction of 54. Even in a nip part between the ink kneading roller 22 and the intermediate roller 26, the pockets 48, 50 are formed. For another moment when the ink kneading roller 22 and the intermediate roller 26 are rotated, and pockets 48, 50 are formed closer to the center part 42 in the axial direction.