A composition for use in amplifying cDNA synthesized by a reverse transcription reaction and detecting RNA that serves as a template of the reverse transcription reaction, the composition containing a thermostable DNA polymerase, a thermostable ribonuclease H, and an intercalating dye. Since the composition of the present invention can suppress the influences to the nucleic acid amplification reaction by RNA that serves as a template for cDNA synthesis, the composition is useful in the detection of RNA, and more useful in quantification of RNA having a desired sequence by real-time RT-PCR.