Disclosed is soft magnetic alloy powder for electromagnetic and magnetic shield, which can be easily flattened and exhibits good performance over a high frequency band, and a shielding member of good shield effect prepared by dispersing the powder in a matrix of rubber or plastics. Powder of a soft magnetic alloy, which consists essentially of, by weight %, Cr: 0.5.0-20%, Si: 0.01-0.5%, Al: 0.01-20% and the balance of Fe and inevitable impurities, is flattened in an attritor, and is added to the matrix material at a content of 30 wt. % or higher, preferably, as high as possible, and processed to form sheets or molded articles. The shielding member of particularly high flame resistance is prepared by adding soft magnetic alloy powder of alloy composition consisting essentially of, by weight %, Cr: 5-14%, Si: 0.01-0.5%, Al: 0.5-20%, and preferably, REM: up to 0.5%, and the balance of Fe and inevitable impurities, after being flattened, is added to a matrix material of chlorine-containing flame resistant rubber or plastics at a high content, and processed to form sheets or molded articles.