Bone conduction device

A bone conduction device comprising:

• an oscillator that is a multilayer flat plate, including a substrate and a piezoelectric layer layered on the substrate, for warping to oscillate in a direction orthogonal to a main surface of the oscillator due to expansion and contraction of the piezoelectric layer;
• a casing having an internal space accommodating the oscillator and a fixing section fixing a circumferential edge of the oscillator, the casing being conductive of oscillations to the outside via the fixing section;
• and
• a signal input unit for receiving a voltage signal input from an external device and applying the voltage signal to the piezoelectric layer, wherein
• the oscillator has a main surface having an entire width longer than an entire width of the fixing section in a direction orthogonal to a direction extending from the fixing section to a center of the oscillator, and
• the main surface of the oscillator has an opening extending in a direction of oscillations for adjustment of a resonance frequency of the oscillator.