PURPOSE: To provide a new peptide useful as an anti-HIV(human immunodeficiency virus) vaccine and as a diagnosing agent for detecting HIV antibody.

CONSTITUTION: This is a portion of a conformational epitope of human immunodeficiency virus(HIV-1) envelope glycoprotein gp 120 which is comprising ≤302 amino acids, the sequences of the BH-10 subtype of the formula, and the analogous sequences from HIV-1 gp 120 isolates other than BH-10. This is obtained, for example, by combining carboxyl terminal amino acids to polystyrene resin, etc., allowing the amino acids constituting the above-mentioned peptide to combine with those amino acids one by one, then by separating the obtained peptide from the said resin, namely by the solid phase chemical synthesis method of Merrifield.