PURPOSE: To make a connection with low loss and high reliability by fixing a couple of optical fibers to be connected by covering both end parts with a sleeve made of glass materials, and by making the connection between the both with core parts aligned after polishing both the end surfaces.

CONSTITUTION: Coating 8 of optical fiber core 6 is removed at one end, and glass fiber 7 is covered with internal sleeve 9a of a glass material and fixed with adhesives or solder glass 10. Coating part 8 and internal sleeve 9a are both covered with external sleeve 9b previously fixed to internal sleeve 9a and the flank is polished with high precision. Thus constituted connection terminal 11 is fixed to fixed holding member 12, and the other connection terminal 11' to movable holding member 13. While the connection part is observed through light source 17 and microscope 18, fine movement members 14 and 15 are adjusted to align axes of cores, which are connected with solder glass or fusion-bonded through discharging, etc. Consequently, the connection with a low loss and high precision are made.