A suction device for an ejection head provided with a nozzle includes a cap capable of sealing a nozzle surface provided with the nozzle, a decompression pump serving as a decompression device, and a suction passage provided between the cap and the decompression pump. The negative pressure level of the suction passage set by the decompression pump are controlled on the basis of a volume of the suction passage such that a liquid with which the ejection head has been filled is sucked out from the nozzle.