To provide a ferrule holder in which air is prevented from whirling into the holder and in which an injected adhesive collects in an expanded diameter part without sticking out of the holder, hardens and improves the adhesive strength, by expanding the diameter of the optical fiber-inserting passage of the ferrule holder, making the expanded diameter part creating a space around the optical fiber, and thereby improving air escape when the adhesive is injected as well as collecting the adhesive after the air goes out.

An inserting port is expanded in the optical fiber-inserting passage of the ferrule holder, providing the expanded diameter part whose diameter is larger than that of the optical fiber.