We have performed a theoretical study on the case of transmission-type one-dimensional magnetophotonic crystals (MPCs) to establish a practical magneto-optical isolator (MOI) that operates properly even in the presence of construction errors. We have introduced a very thin MPC structure with high transmittance and a large Faraday rotation, with the capability of adjusting to a perfect MOI. A minor thickness error for the individual layers of this MOI may take it from being a perfect MOI; however, its adjustability can provide a stable operation against fabrication errors.