To provide a diaphragm valve capable of reliably preventing excessive fastening in valve closing, and excellent in operability and workability.

A step part is provided in a sleeve 6 of a diaphragm valve provided with a valve main body 1 provided with an inlet passage 2, an outlet passage 3 and a partition wall 4 positioned in the intermediate part between these passages 2, 3 and for bending the passages, the sleeve 6 supported by a bonnet 5 fixed on the upper part of the valve main body 1, provided with an internal thread part 8, and not to be axially moved but rotated, a stem 7 provided with an external thread part to be screwed to the internal thread part 8 of the sleeve 6 and to be axially moved with the rotation of the sleeve 6, a compressor 9 fixed on the lower end of the stem 7, and a diaphragm 10 pinched between the valve main body 1 and the bonnet 5, fixed to the compressor 9 and to be brought in contact with or separated from the partition wall 5 by the movement of the stem 7, a small external thread part whose diameter is contracted by the external thread part is integrally provided on the external thread part of the stem 7, and full closing positioning stopper 16 capable of being brought in contact with the step part of the sleeve 6 is screwed and fixed to the small external thread part.