PURPOSE: To eliminate the necessity of sealing with a filler and removal of a sealing material, by thinly applying a ultraviolet curing adhesive to a transparent plastic channel board by a screen coating method, and curing the adhesive by ultraviolet irradiation.

CONSTITUTION: After blanking from a transparent plastic material, cover member forming 2 and channel forming 3 are carried out. Then, annealing 4 is carried out. Then, degreasing, washing and wet sanding 5 are carried out, and thereafter adhesion 6 is carried out. In the adhesion step, a photo curing resin is uniformly applied to cover members 03 and 03' by a screen coating method, and a channel board 01 is superimposed on the cover members 03 and 03', and then ultraviolet rays are irradiated to the resin to quickly cure the same. According to the method, the adhesive layer may be made thin and uniform, and flow of the adhesive layer may be prevented. Accordingly, it is not necessary to eliminate a sealing material.