Positive electrode active material, comprising: a layered lithium composite oxide enabling the intercalation/deintercalation of lithium, wherein a ratio of peak intensities attributed to and planes obtained from X-ray diffraction analysis using a Cu-Kα ray with respect to the lithium composite oxide satisfies Equation 1 below: 0.131 ≤ I 012 / I 003 ≤ 0.143, wherein the ratio of peak intensities attributed to and planes obtained from X-ray diffraction analysis using the Cu-Kα ray with respect to the lithium composite oxide satisfies Equation 2 below: 0.630 ≤ I 104 / I 003 ≤ 0.698, wherein the ratio of peak intensities attributed to and planes obtained from X-ray diffraction analysis using the Cu-Kα ray with respect to the lithium composite oxide satisfies Equation 3 below: 0.379 ≤ I 101 / I 003 ≤ 0.421, and wherein the lithium composite oxide is represented by Formula 1 below: [Formula 1] Li a Ni 1-(b+c+d+e) Co b M1 c M2 d M3 e O f in which, M1 is at least one selected from Mn and Al, M2 and M3 are each independently selected from Al, Ba, B, Ce, Cr, Mg, Mn, Mo, Na, K, P, Sr, Ti, W, Nb and Zr, M1 to M3 are different from each other, 0.90≤a≤1.15, 0≤b≤0.20, 0≤c≤0.10, 0≤d≤0.05, 0≤e≤0.05, and 1.0≤f≤2.0, wherein the lithium composite oxide at least comprises Li, Ni, Co, and Mn, wherein the molar ratio of Ni calculated by Equation 4 below in the lithium composite oxide represented by Formula 1 is 0.6 or more: Ni (molar ratio) = Ni (mol%)/(Ni (mol%) + Co (mol%) + M1 (mol%) + M2 (mol%) + M3 (mol%)). a layered lithium composite oxide enabling the intercalation/deintercalation of lithium, wherein a ratio of peak intensities attributed to and planes obtained from X-ray diffraction analysis using a Cu-Kα ray with respect to the lithium composite oxide satisfies Equation 1 below: 0.131 ≤ I 012 / I 003 ≤ 0.143, wherein the ratio of peak intensities attributed to and planes obtained from X-ray diffraction analysis using the Cu-Kα ray with respect to the lithium composite oxide satisfies Equation 2 below: 0.630 ≤ I 104 / I 003 ≤ 0.698, wherein the ratio of peak intensities attributed to and planes obtained from X-ray diffraction analysis using the Cu-Kα ray with respect to the lithium composite oxide satisfies Equation 3 below: 0.379 ≤ I 101 / I 003 ≤ 0.421, and wherein the lithium composite oxide is represented by Formula 1 below: [Formula 1] Li a Ni 1-(b+c+d+e) Co b M1 c M2 d M3 e O f in which, M1 is at least one selected from Mn and Al, M2 and M3 are each independently selected from Al, Ba, B, Ce, Cr, Mg, Mn, Mo, Na, K, P, Sr, Ti, W, Nb and Zr, M1 to M3 are different from each other, 0.90≤a≤1.15, 0≤b≤0.20, 0≤c≤0.10, 0≤d≤0.05, 0≤e≤0.05, and 1.0≤f≤2.0, wherein the lithium composite oxide at least comprises Li, Ni, Co, and Mn, wherein the molar ratio of Ni calculated by Equation 4 below in the lithium composite oxide represented by Formula 1 is 0.6 or more: Ni (molar ratio) = Ni (mol%)/(Ni (mol%) + Co (mol%) + M1 (mol%) + M2 (mol%) + M3 (mol%)). M1 is at least one selected from Mn and Al, M2 and M3 are each independently selected from Al, Ba, B, Ce, Cr, Mg, Mn, Mo, Na, K, P, Sr, Ti, W, Nb and Zr, M1 to M3 are different from each other, 0.90≤a≤1.15, 0≤b≤0.20, 0≤c≤0.10, 0≤d≤0.05, 0≤e≤0.05, and 1.0≤f≤2.0, wherein the lithium composite oxide at least comprises Li, Ni, Co, and Mn, wherein the molar ratio of Ni calculated by Equation 4 below in the lithium composite oxide represented by Formula 1 is 0.6 or more: Ni (molar ratio) = Ni (mol%)/(Ni (mol%) + Co (mol%) + M1 (mol%) + M2 (mol%) + M3 (mol%)).