To provide a soft magnetic alloy thin strip not only having high saturation magnetic flux density and low magnetic core loss but also having excellent insulation properties, corrosion resistance and toughness.

The soft magnetic alloy thin strip has a composition represented by Fe100-x-y-zAxByXz(wherein, A represents Cu and/or Au; X represents at least one kind of element selected from among Si, S, C, P, Al, Ge, Ga and Be; and x, y and z respectively represent the numbers expressing the atomic% of the elements and satisfying 0<x≤5, 10≤y≤22, 1≤z≤10 and x+y+z≤25), and includes a matrix wherein fine crystal grains having an average grain size of 60 nm or less are dispersed into an amorphous phase at a volume fraction of 50% or more, and in the range of 30 to 130 mm depth from the surface. Further, the soft magnetic alloy thin strip contains an amorphous layer having a B concentration higher than the B concentration of the matrix.