Abstract: This invention provides a method for monitoring the transcriptional synthesis of RNA, and to an apparatus therefor. Specifically, the invention resides in monitoring the initiation and termination of a transcription reaction for RNA synthesis, as well as the synthesis of full-length RNA by measuring the fluorescence of a pair of oligonucleotide probes of two types having a base sequence that continuously hybridizes to a part of a base sequence of the RNA synthesized by transcription, the pair of oligonucleotide probes comprising a donor probe labeled with an energy donor fluorescent molecule and an acceptor probe labeled with an energy acceptor fluorescent molecule.