The invention discloses a middle slide block device for an elevator, comprising a middle slide block (4), a hollow raising pipe and a raising belt (7), wherein the middle slide block (4) is arranged in the hollow raising pipe, and the raising belt (7) is arranged on one end of the middle slide block; a middle slide block pawl (4-2), a middle slide block parcel (4-3), a middle slide block slide claw (4-4) and an adjustable bolt (4-5) in thread fit with the middle slide block pawl are arranged in the middle slide block (4); the middle slide block pawl forms a radial tapered contact surface which is movably abutted against the middle slide block parcel (4-3); the middle slide block slide claw (4-4) is in thread engagement with the middle slide block parcel (4-3); by means of the rotation of the adjustable bolt (4-5) in thread fit with the middle slide block pawl (4-2), the radial tapered contact surface of the middle slide block pawl pushes the middle slide block parcel to rotate; the rotation of the middle slide block parcel pushes the middle slide block slide claw (4-4) to radially extend by means of thread engagement; and the middle slide block slide claw is clamped and fixed on the end of the raising pipe to drive the raising pipe to rise. The device is convenient to move and install, saves labour, is safe and has high reliability.