In accordance with the present invention, there are provided: a soft magnetic flattened powder having an average particle diameter, excellent sheet moldability, and a high magnetic permeability; and a method for producing the soft magnetic flattened powder. The soft magnetic flattened powder according to the present invention includes an Fe—Si—Al-based alloy, an average particle diameter D50 being 30 to less than 50 μm; a coercive force Hc measured by applying a magnetic field in the longitudinal direction of the flattened powder being 176 A/m or less; the ratio of a tap density to a true density being 0.18 or less; a specific surface area BET value being 0.6 m2/g or more; the amount of contained oxygen being 0.6 mass % or less; and the BET value and oxygen value of the soft magnetic powder satisfying expression (1): [oxygen value/BET value≤0.50 mg·g/m2 (excluding zero)].