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):

        R 1 -O-R 2      (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):

        -(CH 2 CH 2 O) m H     (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.