A method for detecting a vehicle intrusion includes a first signal transmission process for alternately transmitting a first signal of a waveform through a first transmission module and a second transmission module at a predetermined period, a first intrusion determination process for analyzing a reflected wave received in response to the transmitted first signal to determine whether the intrusion occurred, a second signal transmission process for transmitting a second signal of a pulse waveform, upon detecting the intrusion as a result of the first intrusion determination process, a second intrusion determination process for analyzing a waveform of a reflected wave received in response to the transmitted second signal to determine whether the intrusion occurred, and transmitting a predetermined alarm message indicating that the intrusion occurred upon detecting the intrusion as a result of the second intrusion determination process.