A button mechanism includes a casing. A lock hole and an engaging portion are formed and disposed on a bottom of the casing, and a plurality of open slots is formed on a lateral wall of the casing. The button mechanism further includes a plurality of buttons respectively disposed on the corresponding open slots, a fixing component, and a supporting component. An end of the supporting component is engaged with the engaging portion. The supporting component includes a first part whereon a piercing hole is formed. The fixing component pierces through the piercing hole and the lock hole to fix the first part on the bottom of the casing. The supporting component further includes a second part connected to the first part and contacting against the plurality of first buttons for constraining movements of the plurality of buttons relative to the casing.