Provided is a tag peptide in which a protease recognition sequence and an epitope of an antibody against the tag peptide are overlapped and thereby the protease recognition sequence per se is usable for detection or purification. Also provided is a purification method for recombinant proteins using the tag peptide and an antibody thereagainst. A preferable tag peptide comprises a Tobacco etch virus (TEV) protease recognition sequence as the protease recognition sequence, and its examples include a tag peptide comprising the amino acid sequence (1): RX1X2LYX3QGKDG (wherein X1, X2 and X3 may be the same or different and represent any amino acid residue).