If exclusive control is used when carrying out update processing or reference processing to a data buffer in a shared memory among plural arithmetic units, waiting time increases and it is difficult to guarantee a real time property. Accordingly, in a control device for a vehicle, a data buffer is multiplexed, and each arithmetic unit carries out update processing and reference processing to a different multiplexed data buffer. An arithmetic unit that is different from the arithmetic unit executing the data update processing synchronizes one data buffer updated by data update processing, with the multiplexed data buffer, in a shorter time than an execution cycle of the data update processing.