A method of providing an image Completely Automatic Public Turing test to tell Computers and Humans Apart (CAPTCHA), and a server thereof. The method includes: outputting an image CAPTCHA including a plurality of images including a determination object image; receiving an image selection from the image CAPTCHA; determining whether a test of the image CAPTCHA is passed, based on the received image selection; and determining what the determination object image means. The images include a first group of images used to determine whether an accessing party passes the image CAPTCHA test and a second group of images unused to determine whether the accessing party passes the image CAPTCHA test. The second group includes the determination object image. The determining of the pass of the image CAPTCHA test is performed by selecting an image representing a correct or incorrect answer from the first group.