An image-forming apparatus includes an image formation section, a placement unit, a paper feed rotating body, a detecting body, a storage unit, and a determination unit. The detecting body detects the arrival of the paper having been supplied by the paper feed rotating body. The storage unit stores measurement data that is based on a measurement time from the start of paper feeding until when the detecting body detects the arrival. The determination unit finds the average time of the measurement times and, when the average time is longer than a predetermined theoretical time, establishes as the paper-non-feed jam detection time a time obtained by adding the absolute value of the time difference between the theoretical time and the average time to a detection reference time. The determination unit determines whether or not a paper-non-feed jam has occurred with the paper-non-feed jam detection time.