An object of the present invention is to provide a lithium secondary battery which has improved capacity, durability, and the other characteristic as compared with conventional lithium secondary batteries. A plate-like particle or a film for a lithium secondary battery cathode active material has a layered rock salt structure. The lithium ion gateway plane is oriented in parallel with a plate surface, which is a surface orthogonal to a thickness direction of the particle and thus exposed at the plate surface, a plurality of layers are stacked together in the thickness direction, and while the layers have the same crystal axis in the thickness direction, as for the plate surface direction perpendicular to the thickness direction, the layers have different crystal axes.