A microcomputer includes a CPU, a protection information storage configured to store memory protection information specifying an access permission or a prohibited state to a memory space by a program executed by the CPU, a memory access control apparatus configured to determine whether or not to allow a memory access request from the CPU according to the memory protection information, and a reset apparatus configured to invalidate the memory protection information stored in the protection information storage according to a reset request signal output from the CPU to a switching of programs executed by the CPU, the reset request signal being based on a state of execution of the program by the CPU. The reset apparatus sets all valid bit storing fields of a plurality of protection setting registers of the protection information storage to invalid state in response to the reset request signal output by the CPU.