A marker system (1) including a sensor array (21) for detecting a magnetic marker laid in a road, a tag reader (34) which acquires marker position information indicating a laying position of the magnetic marker, an IMU (22) which estimates a relative position of a vehicle by inertial navigation calculation, and a control unit (32) which performs an arithmetic process for identifying a position of the vehicle based on the laying position of the detected magnetic marker, and also identifies the position of the vehicle after passage over the magnetic marker based on a relative position of the vehicle estimated by the IMU (22), thereby allowing stable identification of its own vehicle position without being affected by surrounding environment.