The diurnal variation of the frequency of the first Schumann resonance mode has been studied from three ELF observation sites located at Spitsbergen, the Kola Peninsula, and the Kamchatka Peninsula. The induction magnetometer measured ELF separately in two components: NS (north-south) and EW (east-west). The frequency variation is 0.2–0.3 Hz at all the observatories. The semidiurnal harmonics dominate in the frequency variation. The variation seems to be controlled by the local time (LT) rather than by the universal time (UT). The frequency of the NS component has maxima approximately at 0700 and 1900 LT. The diurnal variation of the frequency of the EW component reveals the antiphase behavior so that the maximum in the EW component frequency occurs at ∼0100 and 1300 LT.