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): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒR 1 -O-R 2 €ƒ€ƒ€ƒ€ƒ€ƒ(1) [wherein R 1 is a hydrocarbon group having 8 - 24 carbon atoms, and R 2 is a group represented by the formula (2): or a group represented by the formula (3): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ-(CH 2 CH 2 O) m H€ƒ€ƒ€ƒ€ƒ€ƒ(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.
