This article introduces the gravity methods for petroleum explorations. Gravitational methods are based on the sensitive measurement at the surface of small variations in the gravitational field, but the measurement technology of land gravimeter has already established. In the present, the new trends of gravity measurement are coming. Gravity measurements by ship and airplane are possible. Therefore, Bouguer anomaly map of Japan map was compiled from about 350, 000 land gravity data, about 1, 000, 000 ship-borne gravity data and altimeter data from satellite in area where observation data are sparse, and the gravity basement of Japan was obtained from these data.New technology, which is capable of accurately measuring the full gravity gradient tensor, has only recently become available in the exploration geophysics domain from military research projects (e. g. the Bell Geospace gradiometer). Gravity gradiometry data have superior characteristics to traditional gravity measurements. The components of the gravity gradient tensor hold much more information about the subsurface than do traditional potential field measurements. Such gravity data can constrain geology in areas where seismic interpretation is difficult, such as sub-basalt and sub-salt. These data are capable of resolving shallow structures, such as the limbs of salt domes, far more accurately than can seismic surveys.