This catheter includes: a longitudinal member； a cover sheath that sheathes the longitudinal member and is movable along a longitudinal axis relative to the longitudinal member； and a manipulable part for subjecting the cover sheath and the longitudinal member to relative movement along the longitudinal axis. A slit extending from the distal end toward the base end side along the longitudinal axis is formed on the outer circumferential surface of the distal end of the longitudinal member. The distal end of the longitudinal member is aligned with the distal end of the slit in the direction of the longitudinal axis, and the distal end of the longitudinal member is formed so that the distal end of the longitudinal member has a diameter that is greater than the inner diameter of the distal end of the cover sheath. The catheter is configured such that when the distal end of the longitudinal member is inside the cover sheath, the distal end of the longitudinal member is pressed by the inner circumferential surface of the cover sheath and elastically deforms, and the opening width of the slit becomes smaller than the opening width of the slit when the distal end of the longitudinal member is projecting from the distal end of the cover sheath.L'invention concerne un cathéter comprenant : un élément longitudinal ； une gaine de recouvrement qui enveloppe l'élément longitudinal et qui est mobile le long d'un axe longitudinal par rapport à l'élément longitudinal ； et une partie manipulable pour soumettre la gaine de recouvrement et l'élément longitudinal à un mouvement relatif le long de l'axe longitudinal. Une fente s'étendant depuis l'extrémité distale vers le côté d'extrémité de base le long de l'axe longitudinal est formée sur la surface circonférentielle externe de l'extrémité distale de l'élément longitudinal. L'extrémité distale de l'élément longitudinal est alignée sur l'extrémité distale de la fente dans la direction de l'axe longitudinal et l'extrémité distale de l'él
