A mobile communication device with replaceable function modules includes a main body and an externally connected device. The main body serves as a central member, and has a main hybrid joint including an electrical contact and a magnetic joint. The main hybrid joint of the main body is joined to a device hybrid joint of the externally connected device, so as to realize the function thereof. When joined together, the main body activates a functional module of the externally connected device functional module. In addition, the main body and the externally connected device are further joined through the magnetic joints. Therefore, when separated by accidentally falling onto the ground, the mobile communication device can be rejoined through the magnetic joints, and thus it is unnecessary to worry about the unavailability due to the break-down of the joint portion.