A vibrating device having tuning fork arms extending in a first direction that are joined to a base portion and are arranged side by side in an second direction. Each of the tuning fork arms has a structure that a silicon oxide layer is laminated on a Si layer made of a degenerate semiconductor, and that an excitation portion is provided on the silicon oxide layer. When a total thickness of the Si layer is denoted by T1, a total thickness of the silicon oxide layer is denoted by T2, and the temperature coefficient of resonant frequency (TCF) when the silicon oxide layer is not provided on the Si layer is denoted by x, a thickness ratio T2/(T1+T2) is within a range of (−0.0002x2−0.0136x+0.0014)±0.05.