By γ-ray spectrometer we measured radioactivity of various samples from domestic oil and gas fields, as we had been under the apprehension of the existense of NORM(Naturally Occuring Radioactive Materials). In Higashi-Kashiwazaki gas field, we detected the feeble radioactivity in sludge and water owing to the subsurface brains. But the maximum of these samples was about 12 Bq/g in safety level. And in other fields we did not measured fatal radioactivity.