PURPOSE: To form a coating film effective in producing an aperture or reflection- type fluorescent lamp by the horizontal method.

CONSTITUTION: A straight glass tube 1 is horizontally held on a horizontal roller 6, a fixed amt. of coating soln. 3 is continuously supplied from one end of the tube 1 toward the other end, the soln. 3 is allowed to flow continuously to a specified depth of the tube 1, and the tube 1 is rotated around its centerline to a specified angle. The amt. of the soln. in the tube 1 and the angle of rotation are fixed, and the soln. 3 is applied on the inner face of the tube 1 except an opening 2 within a specified angle. The rotation of the tube 1 is then stopped, the excess soln. is drawn off from the tube 1, and the soln. 3 in the tube 1 is dried and baked to form a desired coating film.