A method of manufacturing a pneumatic tire has a winding step of forming a rubber ribbon winding body constructing a tread rubber by spirally winding a rubber ribbon obtained by co-extruding a first rubber and a second rubber which are different in hardness. The first rubber is mainly arranged in a first area by making a cross sectional area ratio of the first rubber greater than that of the second rubber. The second rubber is mainly arranged in a second area by making the cross sectional area ratio of the first rubber smaller than that of the second rubber. The cross sectional area ratio of the first rubber becomes progressively smaller in a part of the first area as the second area approaches. The rubber ribbon retains an interface boundary between the first rubber and the second rubber to at least a part of the second area.