The present invention provide a process for sequence-specific nucleic acid amplification capable of improving the detection sensitivity and increasing the signal. In particular, the present invention provides a reagent for nucleic acid amplification containing at least one member selected from the group consisting of EDTA, NTA, UDA, CyDTA, DTPA, GEDTA, TTHA and their salts, specifically a reagent for nucleic acid amplification comprising, in addition to the at least one compound, a forward primer having a DNA sequence homologous to a sequence of a target RNA; a reverse primer having a DNA sequence complementary to a sequence of the target RNA and having a promoter for RNA polymerase attached to its 5' end; ribonucleotides; deoxyribonucleotides; a reverse transcriptase or RNA-directed DNA polymerase; a RNase H; a DNA polymerase or a reverse transcriptase having DNA-directed DNA polymerase activity; and a RNA polymerase. The present invention also provides a process for nucleic acid amplification characterized by carrying out a nucleic acid amplification reaction in the presence of at least one member selected from the group consisting of EDTA, NTA, UDA, CyDTA, DTPA, GEDTA, TTHA and their salts.