Insertion of variant exons of CD44 gene of cancer stem cells into its mRNA is inhibited whereupon the cancer stem cells lose their properties so that they are rendered sensitive to anticancer agents and radiation, possibly leading to cancer treatment.A drug for cancer treatment, comprising an antisense oligonucleotide capable of inducing skipping of variant exon(s) of CD44 gene to thereby increase expression of normal CD44 mRNA, a pharmaceutically acceptable salt thereof, a solvate thereof or a prodrug thereof. An oligonucleotide of 20-23 bp having the entirety or a part of any one of the nucleotide sequences as shown in SEQ ID NOS: 1 to 19, a pharmaceutically acceptable salt thereof, a solvate thereof or a prodrug thereof. A drug for inducing skipping of at least one variant exon selected from the group consisting of variant exons 8, 9 and 10 of CD44 gene, comprising the above-described oligonucleotide, a pharmaceutically acceptable salt thereof, a solvate thereof or a prodrug thereof.