PURPOSE: To provide a method for removing a supernatant by which a supernatant is removed from an ink mixture without convoluting ink and in which operation is automated.

CONSTITUTION: This device is constituted of a disk-shaped shielding plate 2, a pump 1 arranged above the shielding plate 2, an elevating/lowering unit 7 consisting of a head 5 equipped with an ink level sensor 3 and ink rising sensors 4a, 4ba and a lifting/lowering part 6 for supporting the head 5, and a supporting base 10 equipped with a lifting/lowering motor 8 and a driving shaft 9. When the elevating/lowering unit 7 is lowered and the interface is detected by the ink level sensor 3, it is stopped from lowering and a supernatant is sucked by the pump 1. Therefore, when the ink rising is detected, the pump 1 is stopped, the ink convolution is eliminated and the operation is automated.