Magnetic　hyperthermia　ablates　tumor　cells　by　the　heat　dissipated　from　magnetic　nanoparticles　(MNPs)　exposed　to　an　alternating　magnetic　field.　The　applied　magnetic　field　plays　an　important　role　in　magnetic　hyperthermia,　since　both　its　amplitude　and　uniformity　directly　affect　the　treatment　results.　The　amplitude　of　magnetic　field　can　be　easily　set　to　a　required　value　for　reaching　a　desired　maximum　temperature,　but　the　uniformity　requires　a　modification　in　the　experimental　setup.　Although　in　practice　the　magnetic　field　is　not　homogeneous,　most　of　the　previous　reports　generally　assume　it　to　be.　In　this　study,　the　homogeneity　of　the　magnetic　field　is　improved　by　adding　a　third　coil　between　the　original　two　in　the　conventional　Helmholtz　coils.　In　addition,　a　differential　evolution　algorithm　is　used　to　optimize　the　parameters　for　the　improved　coils　by　considering　a　proposed　objective　function.　The　results　of　applying　the　proposed　method　are　evaluated　considering　a　numerical　simulation　model　of　magnetic　hyperthermia　and　compared　with　the　traditional　approach　using　the　effective　volume　percentage　of　therapeutic　temperature　(EVPTT)　as　performance　index.　The　results　demonstrate　that　the　uniformity　in　the　magnetic　field　of　the　proposed　method　is　significantly　better　than　in　the　case　without　considering　the　proposed　optimization.　In　terms　of　therapeutic　efficiency,　the　improved　magnetic　field　will　translate　as　better　temperature　distribution　in　the　tumor　region,　but　the　gains　are　much　more　evident　when　the　tumor　is　away　from　the　coil　center.