Provided is a portable electronic device, including a case and a movable magnetic part. The case has a top plate, an engagement surface, and an accommodating space. The accommodating space is located below the engagement surface. And the engagement surface further has at least one through hole, and the through hole communicates with the accommodating space. The movable magnetic part is capable of be attracted by a magnetic force to perform axial motion displacement relative to the through hole, so as to be selectively exposed out of the through hole or retracted into the through hole. Therefore, the movable magnetic part in the case is capable of being attracted out of the through hole in order to position the another case, and improve magnetic absorption strength and binding stability between the case and the another case.