Disclosed is an apparatus for injecting working liquid into a micro-injecting device and a method for injecting the working liquid into the micro-injecting device. A container filled with the working liquid is in a vacuum chamber connected to a vacuum device, a plurality of cartridges having micro-injecting devices are inserted into the container and the working liquid in the container is filled into heating chambers of each micro-injecting device. Accordingly, the total manufacturing processes can be simplified so as to increase a production yield and the total manufacturing time of the products can be reduced.