A demodulation unit demodulates a received signal in which carrier wave of a navigation message that is modulated according to a BPSK modulation scheme are included. An error detection processing unit performs an error detection process on the demodulation result using an error detection bit that is included in the demodulation result. A verification word generator generates a verification word using the demodulation result and a check code when an error is detected by the error detection process, the check code being determined in advance for each bit of the navigation message based on a predetermined encoding rule. An estimation unit estimates an originating bit of a demodulation error by comparing the verification word generated by the verification word generator with a verification word table stored in a storage unit. A correction unit corrects the demodulation result by inverting the bit values of bits subsequent to the estimated originating bit.