A storage condition setting device searches, from among a plurality of ECUs that reside within an in-vehicle network, for a target ECU corresponding to a diagnostic item that is input to an input unit. In the case that such a target ECU exists, the storage condition setting device acquires from the target ECU equipment information of a vehicle related to storage conditions that correspond to the diagnostic item, and selects and sets as storage condition data in the target ECU only those items that correspond to the equipment information from among the storage conditions.