A backup unit is provided with respect to a nozzle of a print head for printing by injecting ink, and sucks the ink from the nozzle, the backup unit including: a nozzle cap sealing the nozzle by making contiguous contact with the print head; a pump; and an ink path communicating the nozzle cap and the pump; wherein the pump includes: a bellows part having an internal space formed therein; a movable rod fixed to the bellows part and having an ink passage therein; a slide valve provided in the bellows part and slidable with respect to the rod, the slide valve closing and opening a hole provided at one end of the ink passage with respect to the internal space, depending on a position of the movable rod; an ink inlet provided at the other end of the ink passage and communicating with the ink path; and an ink outlet communicating with the internal space depending on a position of the slide valve, the slide valve having a stroke shorter than a stroke of the rod, a volume of the internal space within the bellows part increasing and decreasing as the slide valve makes a reciprocating motion in a direction parallel to a center axis of the rod, the slide valve sucking the ink from the nozzle via the ink inlet by opening the hole of the ink passage to the internal space when the rod is at a position where the volume of the internal space is a maximum, and discharging the ink in the internal space via the ink outlet as the volume of the internal space decreases.