Provided is a microprocessor including a complex-MAC unit that operates in response to a complex-MAC instruction. The complex-MAC unit receives first and second complex data (each having 2m-bit length) from a first register having a register length of at least 2m+1 bits, and also receives third and fourth complex data (each having 2m-bit length) from a second register having a register length of at least 2m+1 bits, to calculate a sum of real parts or imaginary parts of a complex product of the first and third complex data and a complex product of the second and fourth complex data. The complex-MAC unit adds the obtained sum of the real parts or imaginary parts to a stored value of the third register, and overwrites the third register with the cumulative total value. The third register has a register length of at least 2m+2 bits.