Amphiphilic block polydepsipeptides of AB-type and AB(3)-type (hydrophilic A block: poly(sarcosine), hydrophobic B block: poly(L-lactic acid)) were prepared, and the N-terminals were arranged by guanidium or guanidino-peptide nucleic acid for loading siRNA in a reverse polymeric micelle. The amphiphilic polymers were successfully dispersed and assembled into reverse micelles in triglyceride or diisopropyl adipate. With loading siRNA into the core of the polymeric micelles, the micelle size was reduced down to a diameter of 25 nm in the case of the guanidino-peptide nucleic acid used as the capturing site. This small-size reverse micelle may be available for a transdermal drug delivery system (DDS) for siRNA.