A portable electronic device includes a body, a casing, and a resilient element. The casing accommodates the body such that the body can slide within the casing. The casing has an opening through which an electrical connection unit connected to the body protracts out of, or retracts into, the casing. The resilient element has an end connected to the casing and another end abutting against the body. The resilient element exerts a resilient restoring force upon the body in response to the sliding of the body. The casing has a stop structure configured to operate in conjunction with an engagement structure of the body and thereby limit the range of the sliding of the body. The engagement structure can be disengaged from the stop structure to separate the body from the casing. Accordingly, the portable electronic device has multiple uses, namely quick maintenance, easy assembly, body protection, and automatic accommodation.