A rotary die cutter includes a plate cylinder and two bearer members provided at two opposite ends of the plate cylinder. The plate cylinder has a receiving cavity therein and a plurality of annular knife blades formed on an outer cylindrical surface thereof. A plurality of intake ports is defined in the plate cylinder. Each intake port is surrounded by a corresponding knife blade and in communication with the cavity in the plate cylinder. The plate cylinder defines a discharging hole in a periphery wall thereof and in communication with the cavity.