A transition metal-containing composite hydroxide comprises secondary particles having: a center portion of fine primary particles; and an outer-shell portion having a high-density layer of plate-shaped primary particles formed outside the center portion, a low-density layer of the fine primary particles formed outside the high-density layer, and an outer-shell layer of the plate-shaped primary particles formed outside the low-density layer. The composite hydroxide is obtained by a method comprising a nucleation step in an oxidizing atmosphere and a particle growth step, the particle growth step comprising: a first stage of maintaining the oxidizing atmosphere; a second stage of switching to and maintaining a non-oxidizing atmosphere; a third stage of switching again to and maintaining the oxidizing atmosphere; and a fourth stage of switching again to and maintaining the non-oxidizing atmosphere.