PURPOSE: To obtain method and apparatus for measuring the frequency with very high accuracy using GPS where accuracy deterioration (SA) is effected intentionally.

CONSTITUTION: Frequency is measured using 1PPS from a GPS for obtaining the positioning information based on the distance measuring radio waves transmitted from a plurality of satellites. The phase differences Δt(t1), Δt(t2) between the 1PPS (1sec signal) from the GPS and a frequency to be measured are determined at two measuring times t1, t2 having a large interval. Δf/f (f: frequency to be measured, Δf: microshift of frequency) is then determined based on the phase difference Δt(t1), Δt(t2).