Vibrator element, vibrator, vibration device, electronic apparatus, and frequency adjustment method

A frequency adjustment method comprising:

• providing a vibrator element having a vibrating arm, which flexurally vibrates in a normal direction of a plane including a first direction and a second direction perpendicular to the first direction, and has a first surface one of compressed and extended due to the flexural vibration and a second surface one of extended when the first surface is compressed and compressed when the first surface is extended, the first surface being provided with a first mass section, the second surface being provided with a second mass section, and at least one of the first mass section and the second mass section having a portion, which fails to be opposed to the other of the first mass section and the second mass section in a plan view in the normal direction;
• and
• varying amass of at least one of the first mass section and the second mass section, thereby adjusting a resonant frequency of the vibrating arm.