1. A method of managing a reference face database for improving performance of face recognition in a limited memory environment, the method comprising: acquiring a new input facial image; determining a classification condition relevant to the input facial image with reference to classification conditions of facial images previously registered in the reference face database used for face recognition; and if the classification condition relevant to the input facial image is a specific classification condition and a facial image relevant to the specific classification condition is less sufficient than a preset threshold value in the reference face database, selecting the input facial image as an image that can be additionally registered in the reference face database.