A geomagnetic sensor for computing an azimuth and a method thereof. The geomagnetic sensor includes a geomagnetic sensor module, including X, Y and Z axis fluxgates orthogonal to one another, for performing normalization for mapping output values of the X, Y and Z axis fluxgates onto a previously set normalization range using previously set normalization factors, an operation module for performing operation of new normalization factors based on a plurality of normalization values output from the geomagnetic sensor module when the geomagnetic sensor is swung within a previously set range, a tilt sensor module for computing a pitch angle and a roll angle, and a control module for providing the new normalization factors to the geomagnetic sensor module to allow the geomagnetic sensor module to perform renormalization and computing an azimuth using the output values renormalized by the geomagnetic sensor module and the pitch and roll angles computed during the renormalization. Therefore, it is possible to easily compute the normalization factors used for azimuth compensation.