The object of the present invention is to provide a screening method of a new integrase inhibitor being able to inhibit an HIV infection before the reverse transcription step and having a pharmaceutical site of action totally different from those of traditional integrase inhibitors, a new integrase inhibitor being obtainable by the screening method, and pharmaceutical constituents containing the integrase inhibitor and DNA encoding the integrase inhibitor being greatly expected as new remedies for AIDS. A peptide which specifically binds to a peptide at N-terminal domain of retroviral integrase was screened by phage display method, and as a result of the screening, a peptide being able to inhibit the infection and the proliferation of retroviruses such as HIV-1 before the reverse transcription reaction is obtained.