There is provided a crystal oscillator including a vessel main body having a concave portion, a cover bonded to the vessel main body so as to form an encapsulated vessel together with the vessel main body, a crystal blank held within the vessel, an IC (integrated circuit) chip containing an oscillating circuit utilizing the crystal blank and having a plurality of IC terminals on a major surface thereof, a plurality of circuit terminals formed on a bottom surface of the concave portion of the vessel main body at positions corresponding to the positions of the IC terminals, respectively. The IC chip is fixed to the bottom surface of the concave portion of the vessel main body by effecting face down bonding so that the IC terminals are bonded to the circuit terminals through bumps. At least one of the IC terminals is a group-arranged terminal including a plurality of unit terminals commonly connected to one another, and the plurality of unit terminals are s connected to corresponding circuit terminals through respective bumps.