An optical fiber adapter includes a main body and a pair of inner housings. The main body has an accommodation room having opposing first and second openings in an axial direction. First through fourth stop blocks are positioned on the walls or within the accommodation room. Each inner housing is positioned within the accommodation room, and includes a flange having opposing front and back surfaces and a hollow cylinder extending from the front surface of the flange. The flanges of the two inner housings are attached to each other and are positioned between the first and second stop blocks, and between the third and fourth stop blocks. The first, second, third and fourth stop blocks are positioned to restrict a movement of the flanges in the axial direction. The first opening is configured for an optical fiber connector and the two inner housings to insert into the accommodation room.