A portable electronic device includes a tablet PC, a base panel and two supports. Two opposite ends of each support are respectively pivoted to the tablet PC and the base panel through a first pivotal portion and a second pivotal portion. The second pivotal portion includes a shaft rod fastened on one end of the support, a retractable spring, a fixed cam fastened on the base panel, and a rotary cam. The retractable spring, the fixed cam and the rotary cam are sleeved on the shaft rod. The fixed cam includes three first peaks, and a first cave is formed between any two of the first peaks. The rotary cam is rotated along the supports, abutted against the fixed cam and the retractable spring. The rotary cam includes three second peaks, and a second cave is formed between any two of the second peaks.