Abstract: The present invention is to provide means to treat breast cancer and/or mastitis by topically administering a non-steroidal antiinflammatory analgetic agent and/or an anticancer agent and allowing them efficiently to arrive into the mammary gland. The present invention provides an iontophoretic preparation for treating breast cancer and/or mastitis which contains a non-steroidal antiinflammatory analgetic agent and/or an anticancer agent as an active ingredient and has a donor to be applied on a nipple part for topical administration of the active ingredient from the nipple part to the mammary gland by application of electric potential.