An inertial force sensor comprising a detecting element, a drive section, and a processing circuit, the detecting element comprising: a plurality of orthogonal arms each having a first arm extending in a third direction Z and a second arm extending in a second direction Y, wherein a first direction X, the second direction Y and the third direction Z form an orthogonal reference system, each orthogonal arm being formed by connecting a corresponding first arm to a corresponding second arm; a respective mass section connected to an extremity of each second arm; an excitation section (12, 14) configured to excite the mass sections along the third direction Z; and a detecting section (16, 18) configured to output a signal corresponding to displacement of the mass sections along the first direction X and the second direction Y, wherein each first arm of the plurality of orthogonal arms is mutually connected to another first arm, resonance frequencies of vibrations of the mass sections along the first direction X and the second direction Y are set greater than a resonance frequency of vibrations of the mass sections along the third direction Z, the drive section is connected to the excitation section, and configured to input a drive signal to the excitation section, the processing circuit is connected to the detecting section, and configured to detect displacement of the mass sections along the first direction X and the second direction Y based on a signal output from the detecting section, wherein the processing circuit is configured to detect angular velocity around the first direction X based on displacement of the mass sections along the second direction Y, and also detect angular velocity around the second direction Y based on displacement of the mass sections along the first direction X, the difference between the resonance frequency of the mass sections along the first direction X and the resonance frequency of the mass sections along the second direction Y is within a range that a difference in sensitivity outputs of the detected angular velocity becomes within 5%, and wherein the processing circuit is configured to detect displacement of the mass sections along the first direction X during a first period, and detect displacement of the mass sections along the second direction Y during a second period different from the first period. a plurality of orthogonal arms each having a first arm extending in a third direction Z and a second arm extending in a second direction Y, wherein a first direction X, the second direction Y and the third direction Z form an orthogonal reference system, each orthogonal arm being formed by connecting a corresponding first arm to a corresponding second arm; a respective mass section connected to an extremity of each second arm; an excitation section (12, 14) configured to excite the mass sections along the third direction Z; and a detecting section (16, 18) configured to output a signal corresponding to displacement of the mass sections along the first direction X and the second direction Y, wherein each first arm of the plurality of orthogonal arms is mutually connected to another first arm, resonance frequencies of vibrations of the mass sections along the first direction X and the second direction Y are set greater than a resonance frequency of vibrations of the mass sections along the third direction Z, the drive section is connected to the excitation section, and configured to input a drive signal to the excitation section, the processing circuit is connected to the detecting section, and configured to detect displacement of the mass sections along the first direction X and the second direction Y based on a signal output from the detecting section, wherein the processing circuit is configured to detect angular velocity around the first direction X based on displacement of the mass sections along the second direction Y, and also detect angular velocity around the second direction Y based on displacement of the mass sections along the first direction X, the difference between the resonance frequency of the mass sections along the first direction X and the resonance frequency of the mass sections along the second direction Y is within a range that a difference in sensitivity outputs of the detected angular velocity becomes within 5%, and wherein the processing circuit is configured to detect displacement of the mass sections along the first direction X during a first period, and detect displacement of the mass sections along the second direction Y during a second period different from the first period.