A mobile communication apparatus comprises a first SIM card, an anti-theft control circuit, and a transmission control circuit. The first SIM card is engaged with the mobile communication apparatus and has a corresponding first IMSI code. The anti-theft control circuit has a SIM-card-detection module and a subscriber information management module. The SIM-card-detection module is used for detecting whether the first SIM card is replaced by a second SIM card and generating a corresponding detection result. The subscriber information management module is used for storing the corresponding first IMSI code and predetermined contact information. The transmission control circuit is used for transmitting data and/or signals. When the SIM-card-detection module generates the detection result, the transmission control circuit will send a notice signal according to the predetermined contact information.