To provide a pattern projector which is stably attached to a photographic lens device.

The pattern projector 10 is constituted so that a part deformed by slittings 60 and 60 are deformed including a coupling ring 58, since the slittings 60 and 60 are formed long not only at an annular attaching part 56, but also over a part from the part 56 to the coupling ring 58, when reducing the diameter of an annular attaching part 56 by a clamp ring 64. Thus, since the turning radius R of the attaching part 56 in the case of reducing the diameter of the attaching part 56 gets long, the diameter of the attaching part 56 is reduced in a state where its original posture surface-contacting with the lens barrel front end 13 of the lens device 12 is kept, so that the press-contact part of the attaching part 56 to the lens device 12 becomes a surface-contact state, and then the pattern projector 10 is stably attached to the lens device 12.