To provide a catheter easily and reliably administering a pharmaceutical to a predetermined area in the vicinity of the surface of an internal organ.

This catheter 10, to be attached to the internal organ 4 of the mammal including a human, includes a supporter section 1 whose back surface at least partially adheres to the surface of the internal organ 4, and which is flexible at least partially, and a flexible tube 2 which extends from the surface of the supporter section 1. The supporter section 1 is positioned and fixed to the internal organ 4 as if wrapping the internal organ 4, the back surface of the supporter section 1 has an opening 12 communicated with an internal path of the tube 2, the back surface of the supporter section 1 is formed with an adhesion area adhering to the surface of the internal organ 4, and a non-adhesion area formed of a connection section 11 and non-adhering to the surface of the internal organ 4, and the pharmaceutical is administered from the non-adhesion area.