NOVELTY - A negative electrode active material for non-aqueous electrolyte secondary battery cell (100) comprises composite having carbonaceous material, silicon oxide dispersed in the carbonaceous material, and silicon dispersed in the silicon oxide, where a half-value width of a diffraction peak of Si (220) plane in powder X-ray diffraction measurement of the composite is 1.5-8 degrees , a mean size of silicon oxide phase is 50-1000 nm, and a value of (a standard deviation)/(the mean size) is less than or equal to 1 where the standard deviation of a size distribution of the silicon oxide phase is defined by (d84%-d16%)/2.    USE - As negative electrode active material which is useful for non-aqueous electrolyte secondary battery cell; and for battery pack (claimed). The battery pack is useful for power source of digital camera and for an on-vehicle type power source of two-wheeled to four-wheeled hybrid electric vehicle, two-wheeled to four-wheeled electric vehicle, or assisted bicycle.    ADVANTAGE - The negative electrode active material has large capacity and excellent cycle characteristics; has a particle diameter of 5-100 mu m; has a specific surface area of 0.5-10 m2/g; and exhibits stable characteristics when the particle diameter and specific surface area of the active material fall in the above ranges, even though these values affect the rate of the intercalation and deintercalation reaction of lithium, and have a great influence.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) non-aqueous electrolyte secondary battery cell comprising negative electrode including the negative electrode active material, positive electrode including positive electrode active material, and non-aqueous electrolyte;    (2) battery pack comprising the non-aqueous electrolyte secondary battery cell; and    (3) preparing the negative electrode active material involving mixing SiO powder having a mean particle diameter of 50-500 nm with carbon precursor or carbonaceous material in liquid-phase dispersion medium, drying and solidifying resultant mixture, and sintering the dried and solidified mixture.    DESCRIPTION OF DRAWING(S) - The figure shows an exemplary section view of the flat-type non-aqueous electrolyte battery cell.    Wound electrode group (1)    Pouch-shaped case (2)    Negative electrode terminal (6)    Positive electrode terminal (7)    Non-aqueous electrolyte secondary battery cell (100)