The invention discloses a sit-up fitness device which comprises a front supporting rod, a front supporting frame, a connector, a sit-up plate supporting frame, a sit-up plate, a rear supporting rod and a guide rail. The sit-up fitness device is characterized by further comprising a timing statistics displayer and a sit-up plate height adjusting mechanism. Compared with the prior art, the sit-up fitness device is designed through improvement and innovation as the following aspects: the front supporting frame is of a retractable structure; the timing statistics displayer is additionally arranged, placing grooves can be used for placing electronic playing devices with a music playing function, a sporter can listen to music in the process of sporting, sporting fun is improved, and besides the sporter feels happy; the sit-up plate height adjusting mechanism is additionally arranged to adjust the height of the sit-up plate in an electric mode, the adjusting process is simple, efficient and rapid, and the user does not need to leave from the sit-up fitness device. The sit-up fitness device is convenient to use efficiently, strong in function, easy to widely popularize and use, perfect and reasonable in structure and good in fitness effect and increases numerous user-friendly designs.