A microcontroller capable of improving processing performance as a whole by executing different programs by a plurality of CPUs and capable of detecting abnormality for safety-required processing by evaluating results of the same processing executed by the plurality of CPUs. A plurality of processing systems including CPUs and memories are provided, data output from the CPUs in each of the processing systems is separately compressed and stored by compressors for each of the CPUs, respectively. The compressed storage data is mutually compared by a comparator, and abnormality of processing can be detected when the comparison result indicates a mismatch. Even when the timings by which the same processing results are obtained are different when the plurality of CPUs asynchronously execute the same processing, the processing results of both of them can be easily compared with each other since compression is carried out by the compressors. Moreover, since the comparison of the comparator is enabled when comparison enable is given from all the CPUs, the comparison operation result can be obtained based on the timing at which the results of compression by the plurality of compressors are determined.