 has for example a CPU, RAM and ROM. A relationship between values (digital values) of the sin signal and the cos signal and the rotor angular position θ is stored in the ROM in the form of a table. The second microcomputer 000 samples the signal outputted from the sin output coil 000 and the signal outputted from the cos output coil 000 with the sample-hold circuits and A/D-converts them to obtain a sin signal and a cos signal. It then refers to the table stored in ROM and reads out a rotor angular position θ corresponding to the instantaneous values of the sin signal and the cos signal. 