A medium storage device includes: a safe having, at a rear portion, an entrance for replenishment and recovery to which a transit cassette is connectable; an identification unit serving to identify whether a medium is a normal medium or a rejection medium; a temporary holding unit configured to temporarily accommodate a medium; a recycle cassette configured to accommodate the medium identified as the normal medium; a conveyance path configured to convey the medium between the identification unit, the temporary holding unit, and the recycle cassette; a control unit configured to control the conveyance path such that the medium replenished from the transit cassette is conveyed to the temporary holding unit, the medium conveyed to the temporary holding unit is conveyed to the identification unit, and the medium identified as the normal medium in the identification unit is conveyed to the recycle cassette.