We conducted the magnetic survey of hydrothermal vents in the Tofua arc, the Lau Basin, the south west pacific ocean. Sea surface magnetometer (SeaSPY 300) and deep-towing magnetometer (SeaSPY 6000) used for the magnetic survey of this cruise. Deep-towing magnetic survey was performed only TA09 seamount of the surveyed seamounts at a constant altitude of 50~60 m over the seabed. Magnetic anomaly and magnetization of TA09 and TA19-2, known as potential areas of hydrothermal vents, were analyzed for the development of mining. Magnetic anomaly of TA09 shows simple dipole anomalies and high anomalous zone is located at the center of the seamount in the magnetization map. The magnetization map of TA 19-2 shows a high anomalous zone over the summit of the seamount and low anomalous zones over the flank. The magnetic anomaly pattern of TA19-2 is similar to the magnetization pattern. The fracture zones occur at the eastern and western boundaries in the seismic profiles over the center of the caldera of TA 19-2. Magnetic anomaly amplitude from deep-towing magnetometer is ten times more than that from sea surface magnetometer in TA09. Considering morphology of seamounts, low magnetization zones, attributable to hydrothermal vents, are located over summit, caldera and caldera rims. In the future, precision analysis of magnetic anomaly of another seamounts and comparison of other geophysical and geological results will be needed to predict presence and location for the development of hydrothermal vents.