A geomagnetic sensor with 3-axis acceleration sensors is provided. The geomagnetic sensor a geomagnetic measurement module including flux gates of X, Y and Z axes mutually crossing at right angles, a tilt measurement module including acceleration sensors of X, Y and Z axes mutually crossing at right angles, a tilt calculator primarily calculating a pitch angle and a roll angle using output values of each acceleration sensors of the X and Y axes, and performing second calculation by adjusting at least one of the primarily calculated pitch angle and roll angle using an output value of the acceleration sensor of the Z axis, and a controller calculating an azimuth using the readjusted pitch angle and roll angle and an output value of the geomagnetic measurement module. Accordingly, the pitch angle and roll angle are precisely measured to calculate the azimuth.