According to one embodiment, a klystron device includes a klystron body and a focusing magnetic field device. The klystron body has an electron gun section, a collector section, a plurality of cavity resonators, and a plurality of drift tubes. The cavity resonators have nose sections that face each other in an axial direction and form a gap section that is connected to the drift tubes. At least one of the cavity resonators has an electric field correction section in a part of the nose section that makes a space of the gap section different with respect to a space between the nose sections.