A method of producing a PCR amplification product is provided that suppresses an effect of precipitate, turbidity, or the like derived from a whole blood sample on a detection in the detection of an amplified nucleic acid by an optical unit. The amplification product complementary to a target nucleic acid in the whole blood sample is produced by PCR in a condition where a ratio of the whole blood sample in a PCR reaction solution is in the range of 0.1 to 0.9% by volume or 0.01 to 1.8 g/L in term of hemoglobin content. When the PCR is carried out with such conditions, even with an untreated whole blood sample, a monitoring of the amplification product by the optical unit can be done while suppressing the effect of the precipitate or the turbidity.