A method of manufacturing a power transmission belt having a body with a length and a cushion rubber layer in which at least one carrying member is embedded so as to extend lengthwise of the body. The method includes the steps of: extrusion molding (a) a first rubber composition including rubber with short fibers therein and (b) a second rubber composition that is different than the first rubber composition to produce a first sheet in which the second rubber composition defines at least a part of the cushion rubber layer; applying the at least one load carrying member to the second rubber composition to produce a preform assembly; and processing the preform assembly to produce a power transmission belt.