[en] Hysteresis losses in a multifilamentary Nb₃Al/Cu composite superconductor have been examined by means of measuring magnetization. The Nb₃Al conductor consists of 397 Nb₃Al filaments, whose diameter is 21 μm, embedded in the copper matrix. The non-copper critical current density is 510 A/mm² at 12 T which is the same level as that of commercial Nb³Sn conductors. Magnetization measurements of the Nb₃Al conductor have been performed in the parallel and perpendicular fields. For the field perpendicular to the conductor length. It was shown that the effective filament diameter is almost equal to the actual filament diameter. On the other hand, the hysteresis loss for the field parallel was around one-fourth as large as that for the perpendicular, corresponding to the effective filament diameter of approximately 8 μm. The reason for this result is considered to be that the Nb₃Al layer produced between Al and Nb sheets after reaction is in a whirlpool state, and it shows that the Nb₃Al conductor is fully available for application to magnets in fusion machines such as ITER, which are operated in a pulsed field