The utility model provides a transmission device for regulating electronic declination angle of an antenna and a tunable antenna employing the transmission device. The transmission device comprises an electric regulating module, a manual regulating module, a scale and a sensor, wherein the electric regulating module comprises an electric transmission unit and an electric driving unit connected with the electric transmission unit, the manual regulating module comprises a manual transmission unit and a manual driving unit connected with the manual transmission unit, one end of the manual transmission unit is inserted into one end of the electric transmission unit to ensure synchronous transmission in a same direction, and the scale and the sensor are respectively connected with the electric transmission unit or the manual transmission unit and mark same moving distance when driven by the electric transmission unit or the manual transmission unit. The utility model further provides a tunable antenna employing the transmission device. The transmission device improves the accuracy of regulating the electronic declination angle of an antenna, and allows closed-loop feedback. The position is fed back synchronously after phase shifter in the antenna is manually or electrically adjusted to ensure the synchronous read of electronic declination angle.