Microprocessor saving data stored in register and register saving method

A microprocessor which realizes fast register saving and restoring which are involved in subroutine calls, and is capable of reducing the scale of a program. A register file is provided with at least one register for storing data to be used for computational processing. A saving memory stores therein data saved from the registers. A saving control unit saves data from a writing destination register to the saving memory when an instruction to write to the register is executed in a subroutine. Then the saving control unit restores data saved in the saving memory back to the original registers when an instruction to return from the subroutine is executed.