A negative electrode active material comprising silicon oxide satisfying the following Equation 1 and Equation 2 when solid state NMR (29Si-DDMAS) of silicon is measured for the silicon oxide after performing charging at least once is excellent in the performance as a negative electrode active material for a lithium secondary battery; 0.42≤S1/(S1+S2+S3)≤0.55  (Equation 1) 0.21≤S3/(S1+S2+S3)≤0.26,  (Equation 2) in which S1 is a sum of peak areas of a group of signals assigned to Si having a Si—Si bond and having peaks at 0 to −15 ppm, −55 ppm, −84 ppm and −88 ppm, S2 is a sum of peak areas of a group of signals assigned to Si having a Si(OH)4-n(OSi)n (n=3, 4) structure and having peaks at −100 ppm and −120 ppm, and S3 is a sum of peak areas of a group of signals assigned to Si having a Si(OLi)4-n(OSi)n (n=0, 1, 2, 3) structure and having peaks at −66 ppm, −74 ppm, −85 ppm and −96 ppm.