PROBLEM TO BE SOLVED: To provide an indwelling needle with a simple structure which can perform supply of a medicinal solution or the like without retention and further facilitates checking of a back flow of blood.SOLUTION: An indwelling needle includes: an outer needle 2 an outer needle base 4 which has a female luer 7 at a rear end part and a cylindrical space 8 at an intermediate part a rubber stopper part 5 which is fitted in the cylindrical space 8 and slidably moves between a first position and a second position and a chamber part 6 fixed in the cylindrical space 8. When the rubber stopper part 5 is located in the first position, a rear end of the chamber part 6 makes contact with a partition wall 16 of the rubber stopper part 5. Then, when a male luer 24 is connected to the female luer 7, the rubber stopper part 5 is pushed by the male luer 24 and moves to the second position. Further, a rear end side of the chamber part 6 pushes and opens a slit valve 15 of the partition wall 16, and protrudes in the back of the partition wall 16.
