A miniaturized all-metal slow-wave structure includes: a circular metal waveguide; and metal electric resonance units provided in the circular metal waveguide; wherein the metal electric resonance unit provided in the circular metal waveguide includes a ring-shaped electric resonance metal plate with an electron beam tunnel provided on a center thereof, and a ring plate body of the ring-shaped electric resonance metal plate has two auricle-shaped through-holes symmetrically aside an axial-section; a main body of the auricle-shaped through-hole is a ring-shaped hole, two column holes extending towards a center of a circle are provided at two ends of the ring-shaped hole; the ring-shaped electric resonance metal plates are perpendicular to an axis and are provided inside the circular metal waveguide with equal intervals therebetween, external surfaces of the ring-shaped electric resonance metal plates are mounted on an internal surface of the circular metal waveguide.