Photogating　effect　based　on　vertical　structure　of　2D　materials　allows　for　the　realization　of　a　highly　sensitive　photodetector.　A　highly　sensitive　and　broad-spectrum　(365-965　nm)　photodetector　is　reported　based　on　the　indium　selenide　(InSe)/rhenium　disulfide　(ReS2)　vertical　heterostructure,　where　the　top　layer　InSe　serves　as　the　photogate　to　regulate　the　channel　current,　enabling　a　large　photoconductive　gain　of　10(6).　The　detectivity　of　the　photodetector　can　reach　6.51　x　10(13)　Jones,　making　this　one　of　the　highest　values　among　reported　transition　metal　dichalcogenide　photodetectors.　The　photodetector　represents　a　high　responsivity　of　1921　A　W-1,　an　ultrahigh　external　quantum　efficiency　(EQE)　of　6.53　x　10(5)%,　and　a　fast　response　time　of　21.6　ms.　The　outstanding　properties　of　the　InSe/ReS2　heterojunction　reveal　the　promising　potential　in　high-efficient,　ultrasensitive,　broadband　photodetectors.