A sit-up bench apparatus includes a base set, two supporting rod sets, two elastic sets and an extending rod set. The base set includes a seat body and a pivotal base. The aperture is formed at one end of the pivotal base. The supporting rod set is pivotally disposed at the pivotal base and includes a supporting rod and a first cylinder. The first cylinder is connected with the supporting rod. The elastic set is disposed at the pivotal base and connected between the two supporting rod sets and the base set. The elastic set includes a spring and an extending rod set. One end of the spring is coupled to the pivotal base. The extending rod set is disposed in the aperture and includes a supporting wheel disposed at one end of the extending rod set.