The present invention provides a transmission combined structure of an electric toothbrush including a transmission shaft and a motor. One end of the transmission shaft has a first sleeve, the first sleeve has a first joint, the motor has a rotating shaft, and the rotating shaft A second shaft sleeve is provided, and the second shaft sleeve has a second joint part, and the first and second joint parts have corresponding cross-sectional shapes and corresponding joints； thereby, a better transmission combination structure and effect are achieved.本創作提供一種電動牙刷的傳動結合結構係包含一傳動軸及一馬達，該傳動軸一端具有一第一軸套，該第一軸套具有一第一接合部，該馬達具有一轉軸，該轉軸設有一第二軸套，該第二軸套具有一第二接合部，該第一、二接合部具有相應的截面形狀對應接合；藉以達到較佳的傳動結合結構及效果的功效者。
