An all-metal casing structure includes a casing unit, a first substrate unit, a second substrate unit, an antenna unit and a conductive unit. The casing unit includes at least one metal casing having at least one through opening. The first substrate unit includes at least one first substrate body disposed in the metal casing and neighboring to the through opening. The second substrate unit includes at least one second substrate body disposed in the metal casing and neighboring to the first substrate body. The antenna unit includes at least one antenna module disposed on the first substrate body and corresponding to the through opening, and the antenna module is electrically connected to the second substrate body. The conductive unit includes at least two conductive elements separated from each other by a predetermined distance and electrically connected between the metal casing and the first substrate body.