The present invention addresses the problem of providing a transmucosal absorption promoter for a drug. This problem is solved by using at least one member selected from the group consisting of: (component a) a basic amino acid (component b) a peptide consisting of 2-5 basic amino acids and (component c) tryptophan.本發明之課題在於提供一種藥物之經黏膜吸收促進劑,該課題是透過使用選自於由(a成分)鹼性胺基酸、(b成分)2~5個鹼性胺基酸構成之胜肽及(c成分)色胺酸所構成群組中之至少1種來解決。(無)