NOVELTY - The device (30) has an insulating housing (31) that is provided in coolant circulation line (14). An induction coil (32) generates an induced current and is mounted on outer surface of housing. A high frequency controller (33) generates high frequencies based on a magnitude of a voltage output from fuel cell stack (10) and is provided at outside of induction coil. A heater (34) generates heat by the induced current and is in direct contact with coolant in housing. A connector (35) is connected to high frequency controller to supply power.    USE - Induction heating device for thermal management system of fuel cell system. Uses include but are not limited sports utility vehicles (SUV), buses, trucks, commercial vehicles, watercraft, boats and ships, aircraft, hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles and hydrogen-powered vehicles.    ADVANTAGE - Since the heater is in direct contact with coolant in the housing and the high frequency controller is provided at the outside of the housing, the coolant can be prevented from leaking, hence insulation resistance between the power unit and the heating unit can be ensured. By providing honeycomb cross-sectional structure in heater, the heating surface area of the heater and heat transfer efficiency is increased. The flow length of the coolant is increased by the diaphragm and the contact time between the coolant and heater is increased, so that coolant can be rapidly heated during cold start-up. Since the power consumption of the heater is determined by frequency control of high frequency controller, the power consumption can be controlled based on the voltage of the fuel cell stack, at the same time the occurrence of a reverse voltage can be prevented.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method for rapidly heating coolant in thermal management system of fuel cell vehicle through induction heater.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the thermal management system.    Fuel cell stack (10)    Coolant circulation line (14)    Induction heating device (30)    Insulating housing (31)    Induction coil (32)    High frequency controller (33)    Heater (34)    Connector (35)