Vacuum　sensors　with　small　footprint,　high　sensitivity　and　wide　detection　range　are　important　for　the　vacuum　measurements　in　small　space.　Here,　we　report　a　new　on-chip　nanoscale　vacuum　sensor　(NVS)　based　on　electroformed　silicon　oxide　with　the　structure　of　a　nanoscale　gap　between　two　graphene　electrodes　on　SiO2　substrate.　The　electrical　resistance　of　the　NVS　increases　exponentially　by　a　magnitude　of　two　orders　with　air　pressure　increasing　from　similar　to　10(-1)　Pa　to　similar　to　10(4)　Pa.　The　increase　of　O-2　partial　pressure　is　responsible　for　the　resistance　increase　of　electroformed　silicon　oxide,　where　a　Si-SiOx-Si　tunneling　diode　is　formed.　The　advantages　of　nanoscale　size,　simple　structure,　high　sensitivity,　direct　electrical　readout　and　wide　detection　range　make　the　NVS　promising　for　vacuum　measurement　of　microscale　space.