[Problem] To provide a medical instrument that can discharge a fluid in the state of the position of a discharge section that discharges the fluid being positioned appropriately in a living body, and that can easily supply the fluid to various sites in the living body. [Solution] The medical instrument has: a rigid first elongated member (10) provided with a fluid lumen (10L) through which a fluid (F) can flow and an aperture (11) that opens at the tip end surface a flexible second elongated member (20) provided with an insertion lumen (20L) into which the first elongated member (10) can be inserted and a discharge section (21) that can discharge the fluid (F) and a mobile section (30) that, in the state of the first elongated member (10) being disposed within the insertion lumen (20L) of the second elongated member (20), seals between the first elongated member and the second elongated member, and can cause the first elongated member and second elongated member to move relative to each other in a manner such that the discharge section of the second elongated member is positioned at the tip side of the aperture of the first elongated member.La présente invention a pour but de proposer un instrument médical qui peut décharger un fluide dans létat de la position dune section de décharge qui décharge le fluide qui est positionné de façon appropriée dans un corps vivant, et qui peut acheminer facilement le fluide vers divers sites dans le corps vivant. A cet effet, linvention concerne un instrument médical, qui comporte : un premier élément allongé rigide (10) comprenant une lumière de fluide (10L) à travers laquelle peut sécouler un fluide (F), et une ouverture (11) qui souvre à la surface dextrémité de pointe un second élément allongé souple (20) comprenant une lumière dintroduction (20L) dans laquelle peut être introduit le premier élément allongé (10), et une section de décharge (21) qui peut décharger le fluide (F) et une section mobile (30) qui, dans létat du pr
