A method of manufacturing a piezoelectric resonator unit that includes mounting a piezoelectric resonator on a base member, the piezoelectric resonator including a piezoelectric element and a pair of excitation electrodes facing each other with the piezoelectric element interposed therebetween, each of the pair of excitation electrodes including an underlying layer containing chromium and a surface layer on the underlying layer; forming chromium oxide on the surface layer of each of the pair of excitation electrodes by oxidizing chromium diffused from the underlying layer such that an amount of the chromium oxide is larger on the surface layer of the excitation electrode on a base member side than on the surface layer of the excitation electrode on a lid member side among the pair of excitation electrodes; and joining a lid member to the base member such that the piezoelectric resonator is between the base member and the lid member.