PURPOSE: To obtain an ink supply mechanism capable of supplying ink to the surface of a printing cylinder without causing any uneven supply by a method in which trapped residum of ink supplied to the printing cylinder is mixed with ink newly supplied from an ink box and the trapped ink mixture is circularly supplied.

CONSTITUTION: Ink 2 in an ink box 1 is supplied through a rubber roller G and shaking material rollers F and H to an inking roller A and then supplied to the face 7 of a printing cylinder 6. Residual ink 4 remaining on the inking roller A is sent back to a base roller J and trapped in the contact face between the rubber roller D and the metal roller E, where the residual ink is mixed with ink supplied from the base roller J again, and the ink mixture is continuously and stably supplied to the face 7 of the printing cylinder 6.