The degrees of freedom are increased for the layout for a member (for example, an upper guide or the like that restricts an up-down direction position of a medium) to be disposed above a storage space for storing a paper sheet-shaped medium, and a disposable space for the member is enlarged. A medium storage box having an internal storage space for storing a paper sheet-shaped medium includes an upper installation member (for example, a lid section) that is disposed above the storage space, and a liquid ejection mechanism that ejects liquid from a liquid ejection nozzle. A liquid ejection direction of the liquid ejection nozzle is set in a direction toward a lower face of the upper installation member.