A resonator element includes: at least one resonating arm which performs flexural vibration; a base portion connected to an end of the resonating arm; and a tapered portion which is axisymmetrical with respect to a centerline which bisects the width of the resonating arm, and which has a width increasing toward a portion of the tapered portion connected to the base portion from a portion of the tapered portion connected to the resonating arm, wherein assuming that the length and width of the resonating arm are L and W and the length and width of the tapered portion are Lt and Wt, the shape of the tapered portion is controlled to satisfy a taper length occupancy η=Lt/L and a taper width occupancy ξ=2 Wt/W.