A server divides a plurality of vehicles into groups, transmits control information to an on-vehicle information device of individual vehicles belonging to a group to which a processing turn of the transmission process has come, and receives responses indicating presence or absence of abnormality due to update of on-vehicle devices using the control information from the on-vehicle information device of each vehicle. The server performs the transmission process of the control information toward a group having a following turn when responses indicating presence of abnormality are a predetermined reference value or less, and, suspends transmission processes of control information toward groups having following and subsequent turns when the responses indicating presence of abnormality are more than the predetermined reference value.