A resonator having a base part; and a resonating arm that performs flexing vibration, the resonating arm part has two principal surfaces, a first groove provided on the one principal surface, a second groove provided in juxtaposition with the first groove on the other principal surface, a third groove provided in juxtaposition with the first groove and provided nearer the base part side than the first groove on the other principal surface, and a fourth groove provided in juxtaposition with the second groove and provided nearer the base part side than the second groove on the principal surface. The sum of a depth of the first and second groove part and a sum of a depth of the third and fourth groove part are larger than a distance between the one principal surface and the other principal surface.