A caster for being mounted to a bottom of a device includes a support, a connecting member, and a wheel mounted to the connecting member. The support defines a receiving space. The connecting member is threadedly connected to the support, and comprises a bracket accommodated in the receiving space. The wheel is rotatably mounted to the bracket. The support and the connecting member are operable to rotate relative to each other, with the wheel moving to expose out of or retract inside the receiving space.