Pellets of solid ink are stored in a row vertically in an ink holder of an ink jet printer. The pellets are supplied one-by-one as needed by action of a stopper which supports the pellet stored at the bottom of the holder, and a presser which presses the pellet stored next to the bottom pellet, working together in association with the action of a solenoid. A seal cover, provided at the inlet of an ink container, normally shuts out leaking chemicals from the liquified ink and opens only when the solid ink falls. Deterioration of the liquified ink is thereby prevented. The open-close action of the seal cover is associated with the solenoid action.