An object of the present invention is to provide a transdermal preparation showing more efficient induction of CTL by a WT1 protein-derived cancer antigen peptide.The present invention enables more efficient CTL induction by applying a transdermal preparation containing a WT1 protein-derived cancer antigen peptide, and an ether-type additive represented by the formula (1): R1-O-R2 (1)[wherein R1 is a hydrocarbon group having 8 - 24 carbon atoms, andR2 is a group represented by the formula (2):or a group represented by the formula (3): -(CH2CH2O)mH (3)wherein m is an integer of 1 - 18],wherein the additive is liquid at 20°C, to a WT1 protein-derived cancer antigen peptide.
