A printer, comprising: a lower module including: a paper feeding unit configured to supply paper, and a printing unit configured to print on the paper supplied by the paper feeding unit; an upper module including a stacking unit configured to hold the paper that has been printed on by the printing unit, a pivotable support at a back side portion of the upper module and connecting the upper module to the lower module, the upper module being configured to rotate about the pivotable support back and forth between an open state to a closed state; a first lock portion configured to hold the upper module in the closed state and including a first fastener on the lower module and a first holding portion on the upper module that is movable between a holding position at which the first fastener is held by the first holding portion and a release position at which the first fastener is released from the first holding portion; a second lock portion configured to hold the upper module in the open state and including a second fastener on the upper module and a second holding portion on the lower module that is movable between a holding position at which the second fastener is held by the second holding portion and a release position at which the second fastener is released from the second holding portion; and a link lever on the upper module and configured to reciprocate along a front-to-back direction of the upper module, the link lever, when moving towards a back side of the upper module, causing the first holding portion to move to the release position and the second holding portion to move to the release position. a lower module including: a paper feeding unit configured to supply paper, and a printing unit configured to print on the paper supplied by the paper feeding unit; a paper feeding unit configured to supply paper, and a printing unit configured to print on the paper supplied by the paper feeding unit; an upper module including a stacking unit configured to hold the paper that has been printed on by the printing unit, a pivotable support at a back side portion of the upper module and connecting the upper module to the lower module, the upper module being configured to rotate about the pivotable support back and forth between an open state to a closed state; a first lock portion configured to hold the upper module in the closed state and including a first fastener on the lower module and a first holding portion on the upper module that is movable between a holding position at which the first fastener is held by the first holding portion and a release position at which the first fastener is released from the first holding portion; a second lock portion configured to hold the upper module in the open state and including a second fastener on the upper module and a second holding portion on the lower module that is movable between a holding position at which the second fastener is held by the second holding portion and a release position at which the second fastener is released from the second holding portion; and a link lever on the upper module and configured to reciprocate along a front-to-back direction of the upper module, the link lever, when moving towards a back side of the upper module, causing the first holding portion to move to the release position and the second holding portion to move to the release position.