PURPOSE: To improve roundness and machining precision of an outer size, by a method wherein the outer periphery of a rubber hose is ground concentrically with a core in a way that the core is inserted in an adhering manner through the rubber hose intended to be ground to rotate the hose and the core integrally with each other.

CONSTITUTION: After a rubber hose 30 inserted in a core 1 is rotated in a state to make contact with a rotary roller 3, and a grinding stone 2 is rotated in the same direction as that of the hose 30. Through movement of the grinding stone 2 under rotation by means of a screw 20, the grinding stone is brought into contact with the rubber hose 30 under rotation. With this state, a cylinder 8 is motioned, and a moving table 7 is moved in a direction A. The rubber hose 30 is moved in a longitudinal direction by a distance exceeding a grinding width (l) of the grinding stone 2, a grinding work is applied on the outer peripheral surface of the rubber hose 30 concentrically with the core. As noted above, by applying a machining work in conformity to the outer periphery of the high-precisely machined core 1, the rubber hose 30 can be machined to provide high roundness and a high-precise outer size.