A double-side tuning fork-type bending vibration piece having a basal part, a pair of drive vibration arms, a pair of detection vibration arms, drive electrodes and detection electrodes includes adjustment films of a metallic material or the like formed in connecting areas between the vibration arms and the basal part. The adjustment films are formed in such a way as to cover an area of tapered portions formed in connecting parts between the drive vibration arms and the basal part, an area of the basal part near the tapered portions and an area of the drive vibration arms. While monitoring a detection current outputted from the detection electrodes when the drive vibration arms are excited in driving mode, the adjustment films are partly deleted by laser irradiation so that the detection current becomes 0.