Graphene　has　attracted　great　interest　in　optoelectronics,　owing　to　its　high　carrier　mobility　and　broadband　absorption.　However,　a　graphene　photodetector　exhibits　low　photoresponsivity　because　of　its　weak　light　absorption.　In　this　work,　we　designed　a　graphene/MoSe2　heterostructure　photodetector,　which　exhibits　photoresponse　ranging　from　visible　to　near　infrared　and　an　ultrahigh　photoresponsivity　up　to　1.3　x　10(4)　A　.　W-1　at　550　nm.　The　electron-hole　pairs　are　excited　in　a　few-layered　MoSe2　and　separated　by　the　built-in　electric　field.　A　large　number　of　electrons　shift　to　graphene,　while　the　holes　remain　in　the　MoSe2,　which　creates　a　photogating　effect.