A mobile-terminal detection apparatus that detects a location of a mobile terminal inside a vehicle cabin is provided. The mobile-terminal detection apparatus is configured to receive the radio wave through an interior antenna disposed inside the vehicle cabin; receive the radio wave through a leaky cable disposed inside the vehicle cabin; detect a time difference between a timing of reception of the radio wave from the mobile terminal through the interior antenna and a timing of reception of the radio wave through the leaky cable; and detect, based on the time difference, the location of the mobile terminal relative to a path over which the leaky cable is laid.