A pad mechanism includes a step fixing structure having a plurality of step platforms. A height difference is formed between the two step platforms. A first engaging portion is formed on each step platform. The pad mechanism further includes a pad component having a pad body, a sleeve and a constraining portion. A second engaging portion is formed on the pad body for selectively engaging with the corresponding first engaging portion so as to adjust a height of the pad body protruding from the step fixing structure. The pad mechanism further includes a resilient component sheathing with the sleeve for driving the sleeve, and a constraining component installed on a side of the resilient component and connected to the constraining portion so as to prevent the resilient component from separating from the sleeve.