Nondestructive magnetic testing by magnetic Barkhausen noise and incremental permeability is applied to study the transformation of microstructure of a commercial X210Cr12 steel submitted to laser irradiation. Magnetic quantities are derived to determine the variations of the martensite and retained austenite content observed up to 2 mm in depth to the laser treated surface. Conversion X-ray- Mossbauer measurements in backscattering technique (CXMS) are performed to get an exact phase analysis, including information about phase formation. The magnetic and Mossbauer results are compared in connection with Vickers hardness and metallographic data.