PURPOSE: To accurately conduct desired control without getting out of the timing of interrupting execution even if a program consisting of plural routines is executed and processed at every specified time.

CONSTITUTION: An ECU (electronic control unit to be mounted on a vehicle) is made up of mainly a CPU 11, an ROM 12, an RAM 13 and an input and output device 17 or the like. The value of fACC. B calculated by a 16ms base routine and the value of fACC. I calculated by a 4ms interrupting routing are memorized respectively at an fACC. B memory sphere 132 and an fACC. I memory sphere 133 after each routine processing. The value of fACC. I and the previous value of fACC. decision that is an acceleration quantity increase value for conducting desired control and is memorized at an fACC. memory sphere 131, are compared with each other. The value of fACC. decision is renewed by the difference of these values. As a result, at the ECU, the timing of interrupting execution is not shifted, and also, desired control is conducted accurately.