Abstract: According to the present disclosure, a technology for efficiently introducing a desired foreign substance from the outside of eukaryotic cells into at least the cytoplasm (and the nucleolus) of the cells is provided. A method disclosed here includes a step of preparing a construct for introducing a foreign substance including a carrier peptide fragment composed of any of amino acid sequences: KKRTLRKKKRKKR (SEQ ID NO: 1), KKRTLRKRRRKKR (SEQ ID NO: 2), KKRTLRKRKRKKR (SEQ ID NO: 3) and KKRTLRKKRRKKR (SEQ ID NO: 4), and a foreign substance that is bound to an N-terminal side and/or C-terminal side of the carrier peptide fragment, a step of supplying the construct for introducing a foreign substance to a sample containing desired eukaryotic cells, and a step of incubating the sample to which the construct for introducing a foreign substance is supplied and introducing the construct into eukaryotic cells in the sample.