A vehicular engine control unit has multi-CPU configuration. A main CPU executes a control processing subject to a monitoring processing and transmits monitoring data to a sub-CPU. The sub-CPU executes the monitoring processing based on the received monitoring data. The control processing executed by the main CPU and a control characteristic may be changed or modified in accordance with an engine capacity, a vehicle equipment or the like. Similarly, the monitoring data stored in a memory connected with the main CPU is also changed in accordance with the control characteristic and the like. Therefore, the sub-CPU can be commonly used for several arrangements or the control characteristics of the main CPU.