[Object] It is to provide a method and a kit capable of detecting or quantifying a target RNA simply and rapidly from trace amounts of RNA in a sample, in a case such as when one or more kinds of pathogenic microorganisms are to be detected or quantified.[Solving Means] The method comprises the steps of 1) synthesizing cDNA from a sample containing the target RNA using a liquid-phase primer having a promoter sequence and a reverse transcriptase to obtain a cDNA-RNA complex, 2) degrading the RNA of the complex, 3) synthesizing a double-stranded DNA via the cDNA obtained in the step 2) and the solid-phase primer, 4) synthesizing RNA from the double-stranded DNA, 5) synthesizing cDNA via the RNA obtained in the step 4) and the solid-phase primer to obtain a cDNA-RNA complex, 6) degrading the RNA of the complex obtained in step 5), 7) synthesizing a double-stranded DNA via the cDNA obtained in the step 6) and the liquid-phase primer, and 8) quantifying the double-stranded DNAs obtained in the steps 3) and 7). These steps can be performed in a single reaction solution.