A braking mechanism includes a rack, a receiving member, a braking member, a base seat, a resetting member and an elastic member. Two ends of the resetting member abut the base seat and the receiving member, and the elastic member is positioned between the base seat and the braking member. The elastic member and the resetting member are positioned at opposite sides of the braking member. The base seat includes a first guiding portion, the braking member includes a second guiding portion and an engaging part. The second guiding portion is capable of moving along the first guiding portion under an elastic restorative force of the resetting member and the elastic member, such that the engaging part is engaged with the rack.