We　report　a　giant　effective　magnetic　refrigeration　capacity　in　a　Ni40Co10Mn40Sn10　multifunctional　alloy.　With　a　large　magnetization　difference　between　austenite　and　martensite,　this　alloy　shows　a　strong　magnetic　field　dependence　of　transformation　temperatures.　Complete　magnetic-field-induced　structural　transformation　and　a　considerable　magnetic　entropy　change　are　observed　in　a　broad　operating　temperature　window　of　33　K　near　room　temperature.　Consequently,　an　effective　magnetic　refrigeration　capacity　of　251　J/kg　for　5　T　is　achieved,　which　is　the　largest　value　for　Ni-Mn-based　Heusler　alloys　and　comparable　to　that　of　the　high-performance　Gd-Si-Ge　and　La-Fe-Si　magnetocaloric　materials.　Incorporating　the　advantages　of　low　cost　and　non-toxicity,　this　alloy　shows　very　promising　prospects　for　room-temperature　magnetic　refrigeration.　(C)　2014　AIP　Publishing　LLC.