The purpose of the present invention is to establish a molecular therapy for Alport's syndrome. Provided are the following: a 15 to 30 base-long oligonucleotide formed of a nucleotide sequence complimentary to cDNA of COL4A5 gene, the oligonucleotide having a truncating mutation in COL4A5 gene of an Alport's syndrome patient, and being able to induce the skipping of an exon where the number of bases is a multiple of 3； a pharmaceutically acceptable salt thereof, or a solvate thereof； and a pharmaceutical drug (therapeutic drug for Alport's syndrome) containing the oligonucleotide, a pharmaceutically acceptable salt thereof, or a solvate thereof.
