There is provided an amorphous alloy thin strip having a chemical composition represented by a chemical formula: FexBySiz (x: 78-83 at %, y: 8-15 at % and z: 6-13 at %) capable of stably attaining a low iron loss even when shaped into a wound core, wherein a generation density of air pockets on a face contacting with a cooling roll is not more than 8 per 1 mm2 and an arithmetic mean height Sa on portions other than the air pockets is not more than 0.3 μm.