A positive electrode active material composite for a lithium-ion secondary battery, wherein only on a surface of a lithium transition metal oxide secondary particle composed of one or more of the lithium transition metal oxide particles represented by the following formula: LiNi a Co b Mn c M 1 xO 2... wherein M 1 denotes one or more elements selected from the group consisting of Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Ge; and a, b, c and x are numbers satisfying 0.3 ≤ a < 1, 0 < b ≤ 0.7, 0 < c ≤ 0.7, 0 ≤ x ≤ 0.3 and 3a + 3b + 3c + (a valence of M 1) × x = 3, or the following formula: LiNi d Co e Al f M 2 y O 2... wherein M 2 denotes one or more elements selected from the group consisting of Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Ge; and d, e, f and y are numbers satisfying 0.4 ≤ d < 1, 0 < e ≤ 0.6, 0 < f ≤ 0.3, 0 ≤ y ≤ 0.3 and 3d + 3e + 3f + (a valence of M 2) × y = 3, lithium-based polyanion particles which are represented by the following formula or ': Li g Mn h Fe i M 3 z PO 4... wherein M 3 denotes Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd; and g, h, i and z denote numbers satisfying 0 < g ≤ 1.2, 0 ≤ h ≤ 1.2, 0 ≤ i ≤ 1.2, 0 ≤ z ≤ 0.3 and h + i ≠ 0, and g + (a valence of Mn) × h + (a valence of Fe) × i + (a valence of M 3) × z = 3, and Mn h' Fe i' M 3 z' PO 4... ' wherein M 3 has the same meaning as in the formula; and h', i' and z' in the above formula ' denote numbers satisfying 0 ≤ h' ≤ 1.2, 0 ≤ i' ≤ 1.2, 0 ≤ z' ≤ 0.3 and h' + i' ≠ 0, and (a valence of Mn) × h' + (a valence of Fe) × i' + (a valence of M 3) × z' = 3, and in which a carbon (c) is supported on the surface thereof, are composited with lithium transition metal oxide particles so as to cover the surface of the lithium transition metal oxide particles; wherein an amount of the carbon (c) supported on the surface of the lithium-based polyanion particles is 0.1 mass% or more and less than 18 mass% in 100 mass% of the lithium-based polyanion particles; an average particle size of the lithium-based polyanion particles is 50 to 200 nm; a mass ratio of a content of the lithium transition metal oxide secondary particles to a content of the lithium-based polyanion particles, (:), is 95: 5 to 65: 35, wherein the lithium transition metal oxide secondary particles have an average particle size of 1 to 25 μm, and wherein the average particle size is determined by using an electron microscope. lithium-based polyanion particles which are represented by the following formula or ': Li g Mn h Fe i M 3 z PO 4... wherein M 3 denotes Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd; and g, h, i and z denote numbers satisfying 0 < g ≤ 1.2, 0 ≤ h ≤ 1.2, 0 ≤ i ≤ 1.2, 0 ≤ z ≤ 0.3 and h + i ≠ 0, and g + (a valence of Mn) × h + (a valence of Fe) × i + (a valence of M 3) × z = 3, and Mn h' Fe i' M 3 z' PO 4... ' wherein M 3 has the same meaning as in the formula; and h', i' and z' in the above formula ' denote numbers satisfying 0 ≤ h' ≤ 1.2, 0 ≤ i' ≤ 1.2, 0 ≤ z' ≤ 0.3 and h' + i' ≠ 0, and (a valence of Mn) × h' + (a valence of Fe) × i' + (a valence of M 3) × z' = 3, and in which a carbon (c) is supported on the surface thereof, are composited with lithium transition metal oxide particles so as to cover the surface of the lithium transition metal oxide particles; wherein an amount of the carbon (c) supported on the surface of the lithium-based polyanion particles is 0.1 mass% or more and less than 18 mass% in 100 mass% of the lithium-based polyanion particles; an average particle size of the lithium-based polyanion particles is 50 to 200 nm; a mass ratio of a content of the lithium transition metal oxide secondary particles to a content of the lithium-based polyanion particles, (:), is 95: 5 to 65: 35, wherein the lithium transition metal oxide secondary particles have an average particle size of 1 to 25 μm, and wherein the average particle size is determined by using an electron microscope.