A composite material part and method for manufacturing the part. The part has a large variation in thickness between a first zone having a thickness E1 and a second zone having a thickness E2, which is made as a single part with a transition zone, external surfaces of which have gradients of magnitude, in which the structure of the stack includes; b1) a plurality of continuous plies that extend in the three zones; b2) a plurality of plies that extend in the first zone and in the transition zone, terminating in a stepped manner in the transition zone; b3) a plurality of plies that extend in the first zone and in the transition zone, terminating in a stepped manner in the transition zone.