A manufacturing method of a set of connectors includes: a step of measuring an emitting direction of light emitted from a plurality of ferrules; a step of grouping the plurality of ferrules into a first group or a second group, based on whether the emitting direction is right or left of a straight line connecting a reference fitting portion closest to the emitting direction of the light and an optical axis; a step of fabricating a plug using the ferrule belonging to the first group; and a step of fabricating a receptacle using the ferrule belonging to the second group.