An ameliorating agent for cancer chemotherapy is disclosed, which comprises a chromanol glycoside represented by the following general formula (1) ##STR00001## (wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4, which are identical or different from each other, stand for a hydrogen atom or a lower alkyl group, R.sup.5 stands for a hydrogen atom, a lower alkyl group, or a lower acyl group, X stands for a monosaccharide residue or an oligosaccharide residue optionally having the hydrogen atom of the hydroxyl group in the saccharide residue substituted with a lower alkyl group or a lower acyl group, n is an integer in the range of 0-6, and m is an integer in the range of 1-6).According to this invention, a novel ameliorating agent for cancer chemotherapy is provided which acts safely and effectively in a small dosage to enhance the carcinostatic action of an anti-cancer agent in cancer chemotherapy and repressing side effects by cancer chemotherapy as well.