There are provided a device and method for detecting joint parts of a steel strip in an endless hot rolling process. In particular, there are provided a device and method for accurately detecting joint parts of a steel strip in an endless hot rolling process. The device for detecting joint parts of a steel strip in an endless hot rolling process includes an image signal collection block receiving image signals, each having information on gray level pixels of a steel strip, from a charge coupled device (CCD) camera; an edge line detection block receiving the image signals from the image signal collection block to detect an edge line of the steel strip; a profile calculation block receiving information on the detection of the edge line from the edge line detection block to calculate the sum of gray levels up to an edge line of the steel strip in a traverse direction of the steel strip when the edge line is detected by the edge line detection block; a joint part judgement block receiving information on the sum of the gray levels, which shows a current profile value, from the profile calculation block to judge the edge line as a joint part when a ratio of a mean value of the current profile and a mean value of the previous profile is less than a predetermined value; and an output block receiving information on the judgement of the edge line as the joint part from the joint part judgement block to output a joint part-detecting signal when the edge line is judged to be a joint part.