An in-vehicle device includes a vehicle detection unit that detects behavior of a user's own vehicle that is traveling, a neighboring vehicle detection unit that detects behavior of a neighboring vehicle preceding the user's vehicle, a neighboring vehicle following the user's vehicle, or both of neighboring vehicles, a road determination unit that determines the condition of a road on which the user's vehicle is traveling on the basis of behavior of the user's vehicle detected by the user's vehicle detection unit and behavior of a neighboring vehicle detected by the neighboring vehicle detection unit, and a transmission information creation unit and a transmission unit that transmit road information including a determination result by the road determination unit.