A bag neck sealer includes a base. The base includes an installation wheel, a rotary wheel, a press plate, a movable blade unit and a fixed blade unit. The fixed blade unit has a seat. The seat includes a fixed blade and a protective piece thereon. The protective piece is connected with an elastic member to be against one side of the fixed blade opposite to the seat to shield the edge of the fixed blade. Therefore, when the user operates the bag neck sealer, the user's fingers can be protected from the fixed blade through the protective piece, preventing the fingers from being hurt so as to enhance the safety of the bag neck sealer.