A satellite signal which carries a navigation message including satellite-specific information is received. Data of the navigation message is demodulated from received satellite signal. Error detection processing is carried out on demodulated data on a word basis of the navigation message. The number of bit transitions is counted at each corresponding bit transition position with respect to a first word in which an error is detected in the error detection processing and which carries the satellite-specific information, and plural second words belonging to a different frame from a frame to which the first word belongs and having a common part with the first word. A bit value of the first word is detected based on the number of bit transitions counted.