A bonding structure that provides excellent conductivity and bonding between a piezoelectric body and a metal plate includes a metal plate and an electrode of a piezoelectric body bonded to one another with an electrically conductive adhesive so as to provide electrical conductivity, the electrically conductive adhesive includes carbon black with a nano-level average particle size, and has a paste form included in a solventless or solvent-based resin so that the carbon black forms an aggregate with an average particle size of about 1 μm to about 50 μm. The electrically conductive adhesive is applied between the metal plate and the electrode of the piezoelectric body, and the metal plate and the piezoelectric body are subjected to heating and pressurization so that the carbon black aggregate is deformed, thereby hardening the electrically conductive adhesive.