The present invention relates to a detection method for detecting a target RNA contained in a sample with high sensitivity by using nicking/extension chain reaction system-based isothermal nucleic acid amplification (NESBA) that uses activity of a cleavage enzyme and a DNA polymerase. The NESBA of the present invention is a new concept isothermal target RNA detection method that realizes higher amplification efficiency than the existing NASBA technology and is deemed to be utilizable as a new concept diagnosis technology that can replace conventional target RNA detection technologies.