The piezoelectric resonator element 4, wherein the adjusting part includes a first groove formed from the base portion side of {HEAD ~ the +Z plane} of the resonating arm along the free end direction of the resonating arm and a second groove formed from the base portion side of the −Z plane of the resonating arm along the free end direction of {TAIL ~ the resonating arm}, and an end at the base portion side of the first groove is positioned closer to the base portion than an end at the base portion side of the second groove 
The piezoelectric resonator element 4 , wherein the adjusting part includes a first groove formed from the base portion side of { HEAD ~ the + Z plane } of the resonating arm along the free end direction of the resonating arm and a second groove formed from the base portion side of the −Z plane of the resonating arm along the free end direction of { TAIL ~ the resonating arm } , and an end at the base portion side of the first groove is positioned closer to the base portion than an end at the base portion side of the second groove
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