There is provided a method of adjusting the natural frequency of a dual-axis vibratory structure having: a first spring member having a lengthwise direction coinciding to a first axis direction receiving an electrostatic force; a second spring member having a lengthwise direction coinciding to a second direction perpendicular to the first axis direction and having a width narrower than that of the first spring member; and a mass portion, the method comprising the steps of: measuring the natural frequencies relative to the first axis direction of the vibratory structure and a third axis direction perpendicular to a plane formed by the first and second axes; varying the thickness of the first spring member so as to adjust the natural frequency of the third axis direction while fixing the natural frequency of the first axis direction; and repeating the measuring step and the thickness varying step until the natural frequency of the first and third axes directions are within the scope of a permissible error. The method can be adjusted to coincide the natural frequency of the vibratory structure with a design value, so that linearity and the sensitivity of a sensor are improved and operation bandwidth increases.