An exercising device includes a main frame, a pivot bar pivotally mounted on the main frame, a stop block mounted on the pivot bar and rested on the main frame when the main frame approaches the pivot bar, two rocking bars mounted on the main frame, and two elastic members each biased between the main frame and the pivot bar. Thus, the longitudinal bar of the main frame is rested on the stop block, thereby preventing the main frame from being entirely rested on the ground due to an excessive rotation, and preventing the user's back from being injured due to excessive bending so as to protect the user's safety.