A portable terminal includes a GPS unit configured to receive a GPS signal, a GPS processing section configured to detect GPS accuracy at an interval and detect the position of a vehicle on the basis of the GPS signal received by the GPS unit, and an information processing section configured to detect entrance timing, which is timing when the GPS accuracy is detected when the vehicle is located at an entrance point of a multi-storey parking structure, on the basis of transition of the GPS accuracy detected by the GPS processing section at the interval.