PURPOSE: To obtain a packaging structure of fiber type optical parts which operate stably in a severe environment and have high reliability by using a glass material or solder for fixing a tapered distribution coupling part and completely shutting off the region thereof from the part outer than this region.

CONSTITUTION: A substrate case 1 formed by halving both ends of a glass case opened from one end to the other end is slightly longer in the cover 1a remaining in the central part by halving than the tapered coupling part of two branching devices 2. The two branching devices 2 are housed into the glass case in such a manner that the tapered coupling part is fully covered in the cover 1a and both ends of the tapered coupling part are fixed with low melting glass 5. In addition, these parts are hermetically sealed from outside. The fixing points on both sides thereof are fixed by the ordinary adhesive 4. In brief, the distribution coupling region is shut off from the outside by the low melting glass or solder, thereby the region is completely sealed and fixed. The low melting glass to be used has a softening point of about 400°C which is about half the softening point of ordinary glass.