A positive active material for a lithium secondary battery containing a lithium transition metal composite oxide having a hexagonal crystal structure in which the transition metal (Me) includes Ni, Co and Mn, wherein in the lithium transition metal composite oxide, a molar ratio of Ni to the transition metal (Me) (Ni/Me) is 0.5 or more and 0.9 or less, a molar ratio of Co to the transition metal (Me) (Co/Me) is 0.1 or more and 0.3 or less, a molar ratio of Mn to the transition metal (Me) (Mn/Me) is 0.03 or more and 0.3 or less, and a value obtained by dividing a half width ratio F(003)/F(104) at a potential of 4.3 V (vs. Li/Li+) by a half width ratio F(003)/F(104) at a potential of 2.0 V (vs. Li/Li+) is 0.9 or more and 1.1 or less.