A new micro fluxgate magnetic sensor using micromachined 3-dimensional solenoid coils has been designed, fabricated, and characterized in this work. The fluxgate sensor adopts a ring-type shape and second-harmonic principle, and is composed of exciting coils, a ring core, and sensing coils. Using a newly developed UV lithography-based thick photoresist process and electroplating techniques, planar three-dimensional magnetic fluxgate sensors were fabricated on a silicon wafer. The measured sensor output shows excellent linear characteristics over the range of ±500 µT with a resolution of approximately 60 nT, achieving the sensitivity of 8360 VT 1 • Furthermore, this sensor also shows a wide sensing range of ± 1.5 mT. Using this highly sensitive, on-chip fluxgate sensor, various applications are expected from space research to portable navigation systems.