1ABSTRACTABS becomes popular standard equipment due to increased demand for vehicle safety from user. That trend requests to make ABS smaller in size and lower in cost. Electronic Control Unit of ABS (ABS/ECU) has to correspond to that request and, further, ABS/ECU should lead system development by integration of ECU with actuator in engine compartment. We have been promoting the above development positively as the developer of ECU. This paper describes the development of high temperature-proof and small sized ABS/ECU composed 2 chips with using ASIC (Application Specific of Integrated Circuit) design and the method of thermal design, suitable for integration with actuator.