The invention provides a cartridge-type injection needle and injector. The injection needle cartridge has a substantially columnar retaining member for retaining the injection needle penetrating therethrough and a pair of holder members forming a containing space for containing the retaining member. The paired holding members are formed by a first holder member having a first bottom plate and a first slider section and a second holder member having a second bottom plate facing to the first bottom plate and a second slider section. The containing space is axially extendable and retractable in the state in which the slider sections are alternately displaced along the outer periphery of the retaining member and is not axially retractable in the state in which the extreme end faces of the slider sections face to each other.
