Abstract: The present invention provides a reactor for carrying out in a single container the steps of the extraction of nucleic acids and the amplification of a nucleic acid, the procedures of the steps being usually different to each other. The reactor according to the present invention is a reactor for detecting a target nucleic acid from a sample, comprising at least a first compartment which contains an extraction reagent composition for extracting nucleic acids from said sample, a second compartment which contains an amplification reagent composition for amplifying the target nucleic acid, a separating means for separating the first and second compartments, and an aperture which enables to introduce said sample into only said first compartment.