An object is to improve insulation in a bonding layer and to improve a bonding strength of a supporting body and piezoelectric single crystal substrate, in a bonded body having the supporting body made of a polycrystalline material or single crystal material, the piezoelectric single crystal substrate and the bonding layer provided between the supporting body and piezoelectric single crystal substrate, wherein the bonded body includes the supporting body, piezoelectric single crystal substrate and the bonding layer provided between the supporting body and piezoelectric single crystal substrate, and the bonding layer has a composition of Si(1-x)Ox (0.008≤x≤0.408).