One aspect of the present invention is a positive active material containing an oxide containing lithium and a transition metal element M, in which the transition metal element M is cobalt, iron, copper, manganese, nickel, chromium, or a combination thereof, and in an X-ray diffraction pattern of the oxide, a ratio (Ia/Ib) of peak intensity Ia appearing in a range where 2θ is 20 to 25° and peak intensity Ib appearing in a range where 2θ is 30 to 35° is 0.2 or more and 0.8 or less.