Microcontroller and electronic control unit

A microcontroller in which respective CPUs execute different applications so as to improve processing performance, and the respective CPUs execute an application that requires safety and mutually compare the results thereof so as to enhance the reliability of write data is provided. The microcontroller has a plurality of processing systems made up of a first CPU, a second CPU, a first memory and a second memory, and for the instruction processing about specific processing set in advance, the write to peripheral modules which are not multiplexed is executed twice, and the write data of the first time and the second time are mutually collated.