To provide a GPS compound device having a configuration including a GPS receiver, that accurately determines abnormality in an output from the GPS receiver based on a difference between a GPS pseudorange measurement and a Doppler frequency measurement, when detecting the abnormality in the outputs from the GPS receiver, while avoiding continuation of the abnormality at the time of the abnormality determination resulting from estimation errors of the GPS pseudorange measurement and the Doppler frequency measurement. When the abnormality of the outputs from the GPS receiver are detected, an abnormal period is counted. When the count value is below a predetermined threshold, the outputs from the GPS receiver are treated as abnormal, and after it exceeded the threshold, the outputs from the GPS receiver are treated as normal. Thus, the abnormality of the outputs from the GPS receiver can be determined accurately.