To provide a method for electively amplifying a target nucleic acid and a method for detecting a nucleic acid by said method, which are useful as a method for synthesizing the nucleic acid. A method for amplifying a nucleic acid sequence [EVA (Endonuclease V-dependent Amplification) method] which selectively amplifies a target nucleic acid in a sample, by the use of an oligonucleotide primer containing a base which can be recognized by an endonuclease V, the endonuclease V and a DNA polymerase having a strand displacement activity, and a method for detecting a nucleic acid by said method.