A process for manufacturing a preform, and apparatus therefor, wherein a preform with a branched portion in its cross-section profile is continuously manufactured by delivering a raw form of reinforcing fiber base material with a branched portion in its cross-section profile, among multiple reinforcing fiber base materials for constructing the preform, intermittently in the longitudinal direction thereof; at each delivery discontinuation, performing heat and/or pressure application to the raw base material so as to tentatively obtain a preliminary shaped matter with given configuration; and uniting the obtained preliminary shaped matter with given configuration with raw forms of other reinforcing fiber base materials for constructing the preform.