A rotary mechanism includes a supporter and a bracket. The supporter includes a body, a pivot hole structure and a guiding portion. The pivot hole structure and the guiding portion are disposed on the body. A slot is formed on the pivot hole structure. A top of the guiding portion is a cam structure. The bracket pivots to the supporter. The bracket includes a frame, a constraining portion and a pivoting portion. A bottom of the frame contacts against the guiding portion and slides relative to the cam structure. The constraining portion and the pivoting portion are disposed on the frame. The constraining portion can contact against the body to constrain rotation of the bracket relative to the supporter. The pivoting portion slidably pivots to the slot. The pivoting portion moves along the slot to contact the constraining portion against the body.