A microcontroller in which an increase in hardware is suppressed and data correction capability for software error of RAM can be improved is provided. A microcontroller which performs processing according to a program includes a CPU and a RAM for storing data processed by the CPU, wherein multiplexed regions are defined in the RAM, and when these regions are accessed, an access to an address outputted by the CPU and a copy access to an address obtained by adding or subtracting a certain value to or from the address outputted by the CPU are performed. By this means, the same data can be stored in a plurality of regions and the reliability can be improved.