PROBLEM TO BE SOLVED: To provide a method for simultaneously detecting and quantifying microorganism nucleic acid in a biological sample.SOLUTION: Microorganism nucleic acid is isolated and refined, at least first target nucleic acid, one or more types of primer pairs which specifically hybridize an individual sequence part of the microorganism nucleic acid and an individual sequence part of the target nucleic acid, and reaction mixture including a probe which specifically hybridizes each of sequences amplified by the one or more types of primer pairs are provided, herein, the microorganism nucleic acid and the target nucleic acid hybridize different probes, and the biological sample is added to the reaction mixture. The method is based on amplification of nucleic acid, preferably polymerase chain reaction. A fluorescent signal which is created by an amplified product, and is proportional to concentration of the target nucleic acid and the microorganism nucleic acid is detected and measured, and an amount of
