To provide an air knife which can be assembled easily and accurately.

An air knife comprises a first planar member 18, a second planar member 19 being jointed thereto and forming a knife body 17 in conjunction with the first planar member 18 having a space part 29 being supplied with compressed air between the joint faces, a first inclining face 21 formed on the joint face between the first and second planar members at one end of the first planar member while inclining at a specified angle with respect to the joint face, a second inclining face 27 formed at one end of the second planar member while inclining at a substantially same angle as the first planar member and forming a slit for ejecting compressed air supplied to the space part from one end side of the knife body in conjunction with the first inclining face, and a screw for coupling the first and second jointed planar members at a specified slide position by means of screws.