A vehicle system includes a vehicle-mounted device mounted to a vehicle and a portable device portable by a user, and performs a control to the vehicle corresponding to a collation result performed based on a wireless communication established between the vehicle-mounted device and the portable device. The vehicle-mounted device includes a vehicle-mounted transmission unit which simultaneously transmits radio waves having a predetermined phase difference using at least two transmission antennas disposed orthogonal to each other. The portable device includes a triaxial reception antenna receiving the at least two radio waves, and a magnetic field strength detection unit detecting a magnetic field strength on each of three axes of the triaxial reception antenna. One of the vehicle-mounted device or the portable device includes an illicitness determination unit determining, based on the detected magnetic field strength, whether the wireless communication is established through an illicit repeater.