A power coupling device including a driving coupler mounted in the driving unit having a first connection part and a first positioning part; and a driven coupler mounted in the driven part having a second connection part and a second positioning part, respectively. The driven coupler having a first coupler member fixed to the driven part; a second coupler member having the second connection part and the second positioning part for connection with the first coupler member; and a connection for connecting the first coupler member with the second coupler member to control the connecting position. The connection means has a plurality of projections formed at one of the first and the second coupler members; and a plurality of depressions formed at the other one of the first and the second coupler members.