In a sheet stacking device, a first sheet storage portion and a second sheet storage portion are arranged in alignment in a width direction of a housing, and supported by the housing so as to move in a front-rear direction perpendicular to the width direction. Biasing members are respectively provided on opposite side surfaces of the first and second sheet storage portions, the opposite side surfaces being adjacent and face each other in the width direction. In a first state where the first and second sheet storage portions are moved frontward from the housing, the biasing members abut on each other and bias the first and second sheet storage portions in directions in which the first and second sheet storage portions separate from each other along the width direction.