PURPOSE: To permit the continuous and smooth power transmission without requiring a back-up device by setting the meshing angle of a stepping stage chain for a driving sprocket installed in the transition part where a stepping stage chain transforms from the lower part inclination to the intermediate horizontal part, equal to the inclination angle of an escalator.

CONSTITUTION: Since, in a stepping stage chain sprocket 15, a stepping stage chain 8 is meshed at the part of transition from the lower part inclination to the intermediate horizontal part, the laying angle θ2 of the chain 8 for the sprocket 15 is made equal to the inclination angle θ1 of an escalator. Further, the radius R of the sprocket 15 is set so as to be equal to the radius of curvature in the transition of the chain 8 from the inclined part to the intermediate horizontal part. Accordingly, the laying angle θ2 of the chain 8 for the sprocket 15 can be made equal to the inclination angle θ1 of the escalator, and since the inclination angle θ1 is generally set at about 30°, the laying angle θ2 can be set to about 30°. If this laying angle is kept, the transmission drive between the chain and the sprocket can be made sufficient free from back-up, and the smooth and continuous transmission is achieved.