1. A method for detecting a forged face using an infrared image, comprising: acquiring a first infrared image and first photorealistic image of a current face captured by one camera or two cameras; extracting a face region from the first photorealistic image; analyzing the first infrared image, the analyzing comprising analyzing a quality characteristic of the first infrared image; determining whether the current face is a forged face or not based on a result of the analysis of the first infrared image; and performing a face recognition process on the extracted face region of the first photorealistic image separately from the first infrared image if it is determined that the current face is a non-forged face, wherein analyzing the quality characteristic of the first infrared image comprises: determining a clearness degree of a region of the first infrared image that corresponds to the extracted face region of the first photorealistic image using a sharpness value; and determining the current face to be a forged face or a non-forged face, wherein the current face is determined to be a forged face if, as a result of the determining the clearness degree, the clearness degree of the region in the first infrared image is less than a preset clearness value, and wherein the current face is determined to be a non-forged face if, as a result of the determining the clearness degree, the clearness degree of the region in the first infrared image is identical to or greater than the preset clearness value.