Abstract: Disclosed is a method of manufacturing a pneumatic radial tire comprising the steps of feeding a strip material comprising a plurality of reinforcing cords and having a predetermined width from a standard measure feeding device which is adjustable in its feeding angle to a carrier conveyor, cutting the strip material to a predetermined size in sequence to form strip pieces while alternately moving the strip material and the carrier conveyor intermittently in synchronization with each other, transferring the strip pieces onto the carrier conveyor, forming a belt member having a length equal to a length L of a belt layer for one tire by butting the strip pieces against each other along their longitudinal edges, and using the belt member as the belt layer, wherein if a width of the strip material is A and the number of the strip pieces for forming the belt layer is N, an angle &thgr; for cutting the strip material to the predetermined size relative to a moving direction of the standard measure feeding device is