An image signal format detection apparatus and method. The image signal format detection apparatus includes a first summed absolute difference (SAD) value calculation unit for calculating, from a previous field, a current field, and a next field of a time-consecutive image signal, a first SAD value with reference to pixel values of the current field and the previous field. A second SAD value calculation unit calculates a second SAD value with reference to pixel values of the current field and the next field. A pattern generation unit generates a detection pattern based on a result of a comparison of the first and second SAD values,; and a pattern analysis unit stores the detection pattern by field, compares the stored detection pattern of a series of fields with a predetermined verification pattern, and determines whether the image signal is an image signal produced in 2:2 pull-down. The apparatus detects an image signal produced in 2:2 pull-down by using the SAD values between fields, and can be applied to a deinterlacing device or the like.