To reduce a fluctuation in the rotational speed of a roll in a bath and to reduce surface flaws in the steel strip to be plated, with respect to a driving structure of a roll in a bath dipped into a hot dip plating bath, wherein rotary driving force is transmitted to the roll in the bath by an intermediate shaft connected to one end of the roll in the bath via a joint in the bath, and the joint in the bath has a plurality of torque transmission pins on either side and has torque receiving grooves on the other side.

The part in contact with a torque transmission pin 9 in each torque receiving groove 10 is allowed to have an inclined angle α to a rotary shaft center, or an intermediate shaft 6 is provided with a hollow part, and the force of pushing up a roll in a bath by buoyancy is imparted to the intermediate shaft, so that thrust force for moving the roll 2 in the bath to the intermediate shaft side is extinguished, and further, thrust force of moving the same to the anti-intermediate shaft side is generated.