A semiconductor device has: as security states to which the nonvolatile memory device can transition, an unprotected state in which, when secret information is not set in the nonvolatile memory device, rewriting the nonvolatile memory device is permitted, and reading the stored information is permitted; a protection unlocked state in which, when the secret information is set in the nonvolatile memory device, rewriting the nonvolatile memory device is permitted on condition that a result of authentication using the secret information is correct, and reading the stored information is permitted; and a protection locked state in which, when the secret information is set in the nonvolatile memory device, rewriting the nonvolatile memory device is inhibited until correctness as a result of authentication using the secret information is confirmed, and reading the stored information is inhibited under a predetermined condition.