An in-vehicle gateway device according to an embodiment includes a storage unit, a plurality of internal communication processors, a routing processor and a storage controller. The storage unit stores therein data output by an electronic control unit included in the in-vehicle system. The internal communication processors include an internal communication processor to which at least one electronic control unit is connected. The routing processor transfers data among the internal communication processors and outputs at least a part of the transferred data to the storage unit in a form capable of being stored in the storage unit. The storage controller manipulates or filters, in accordance with a certain rule, at least one of the data to store in the storage unit and the data output from the storage unit.