Cutter mechanism and printer including the same

A printer comprising:

• a main body unit configured to rotatably hold a thermal head by means of a spring configured to bias the thermal head against a platen provided in a opening/closing unit configured to be rotatably fixed to the body unit;
• a print medium conveyance path interposed between the thermal head and the platen;
• a fixed blade unit configured to be attached to the main body unit, including a fixed blade, a fixed blade stay to which the fixed blade is attached, and an elastic biasing member configured to bias the fixed blade stay such that the fixed blade is movable to a fixed blade OPEN state position away from the print medium conveyance path;
• and
• a movable blade unit with a movable blade, configured to be is attached to the opening/closing unit, the movable blade configured to cut a print medium in cooperation with the fixed blade, the fixed blade and the movable blade configured to move to the fixed blade OPEN state position and a movable blade OPEN state position, respectively, away from the print medium conveyance path when the opening/closing unit is in an OPEN state, and the fixed blade configured to be fixed to a position at which the movable blade is movable along the fixed blade to cut the print medium when the opening/closing unit is in a CLOSED state.