A pre-defrosting process for a vehicle comprising: transmitting a signal indicating an estimated departure time calculation request to a server, calculating, by an estimated departure time obtainment unit, an estimated departure time of the vehicle, determining, by a controller, that the current time is earlier than the estimated departure time by a predetermined length of time, wherein the predetermined length of time is greater than the necessary operation period of a defroster for removing frost from a windowpane of the vehicle when a frost formation level of the windowpane is the highest of multiple frost formation levels, obtaining frost formation information, by an information obtainment unit, that is information about formation of frost on a windowpane of a vehicle, calculating, by a frost formation rate calculator, a frost formation rate based on the frost formation information and the estimated departure time, wherein the frost formation rate indicates a frost formation amount of the windowpane, on which frost is formed at the estimated departure time, wherein the frost formation rate calculator is configured to calculate the frost formation level of the multiple frost formation levels, calculating, by an operation period calculator, an operation period of the defroster (R1, R2) needed to remove frost from the windowpane based on the frost formation rate, determining, by an operation start time determination unit, an activation time of the defroster (R1, R2), determining, by the operation start time determination unit, that the activation time is a time earlier than the estimated departure time by the operation period, and transmitting, by a defrosting controller, an operation request signal for starting operation of the defroster (R1, R2) at the activation time. transmitting a signal indicating an estimated departure time calculation request to a server, calculating, by an estimated departure time obtainment unit, an estimated departure time of the vehicle, determining, by a controller, that the current time is earlier than the estimated departure time by a predetermined length of time, wherein the predetermined length of time is greater than the necessary operation period of a defroster for removing frost from a windowpane of the vehicle when a frost formation level of the windowpane is the highest of multiple frost formation levels, obtaining frost formation information, by an information obtainment unit, that is information about formation of frost on a windowpane of a vehicle, calculating, by a frost formation rate calculator, a frost formation rate based on the frost formation information and the estimated departure time, wherein the frost formation rate indicates a frost formation amount of the windowpane, on which frost is formed at the estimated departure time, wherein the frost formation rate calculator is configured to calculate the frost formation level of the multiple frost formation levels, calculating, by an operation period calculator, an operation period of the defroster (R1, R2) needed to remove frost from the windowpane based on the frost formation rate, determining, by an operation start time determination unit, an activation time of the defroster (R1, R2), determining, by the operation start time determination unit, that the activation time is a time earlier than the estimated departure time by the operation period, and transmitting, by a defrosting controller, an operation request signal for starting operation of the defroster (R1, R2) at the activation time.