Since 1978 we have conducted extensive gravity surveys in Central Honshu, Japan, to establish 5,345 new gravity stations. The results are synthesized into a Bouguer anomaly map with the data from other sources. The map shows a distinctive belt of gravity gradient on the Pacific side of Central Honshu. This belt is about 300 km long and 30--50 km wide, across which Bouguer anomaly changes by about 30-50 mGals. Broad Bouguer high prevailing further oceanward of Central Honshu is sharply bounded by this anomaly belt. There seems to be no apparent correlation between this anomaly belt and the surface geology.