A medium stacking apparatus comprises a stacking roller for stacking a medium in a stacking space, a supporting part for supporting a lower portion of the medium transferred by the stacking roller, a plurality of stacking guides for supporting the medium disposed on the supporting part in a standing state, a plurality of moving devices for moving the plurality of stacking guides, and a control part controlling the plurality of moving devices. The control part controls the plurality of moving devices to move a second stacking guide toward a first stacking guide to allow the stacked medium to stands up in a state where the medium is supported by the first stacking guide of the plurality of stacking guides.