A route searching method is provided which allows drivers having mutually similar traveling purposes and preferences to find highly convenient routes by sharing their route searching know-how. A center apparatus (1) collects probe data received from an in-vehicle terminal apparatus (5). A preference parameter creating unit (14) calculates, based on the probe data, road usage frequencies according to preference items such as vehicle type, driver age and gender, and travel purpose which can be factors for route selection and stores the calculated road usage frequencies as preference parameters in a preference parameter database (15). A route searching unit (513) included in the in-vehicle terminal apparatus (5) requests the center apparatus (1) to transmit a preference parameter similar to user attribute information (519), adjusts link costs according to the preference parameter received from the center apparatus, and determines a minimum-cost route to a destination.