To provide a method for manufacturing a bundle fiber by which dropping of a sleeve or depression in a part of optical fibers can be suppressed.

The coating layer at the end part of each fiber in a plurality of optical fibers is removed to expose a glass part (step S1). The end part of each fiber in a plurality of optical fibers where the coating layer is removed is irradiated with plasma particles (step S2). The inner wall of a cylindrical sleeve is irradiated with plasma particles (step S3). Then the end part of each fiber in a plurality of optical fibers where the coating layer is removed and the end part is irradiated with plasma particles is inserted into the inside of the sleeve irradiated with the plasma particles (step S4). An adhesive is supplied in the inserted state (step S5) to fix the end part of the plurality of optical fibers to the sleeve with the adhesive so as to manufacture the bundle fiber.