An image signal detecting apparatus and a method thereof capable of detecting a 2:2 pull-down image as well as a 3:2 pull-down image with respect to an input image signal. The image signal detecting apparatus includes a SAD calculation unit for calculating summed absolute differences (SADs) among a current field (n), a previous field (n−1), and a next field (n+1) with respect to consecutively input image signals, a pull-down image detection unit, a still image determining unit , a bad-edit detection unit for detecting a bad-edit in the detected pull-down image, and a decision unit for deciding whether the input image signal is the pull-down image or not based on the result of detecting the pull-down image, the result of determining whether the input image signal is a still image by the still image judgment unit, and the result of detecting the occurrence of the bad-edit.