A positive-electrode active material for a lithium secondary battery, comprising: a secondary particle in which a plurality of primary particles of a lithium composite metal oxide are aggregated, wherein the secondary particle has a void formed therein and a through-hole that connects the void to a surface of the secondary particle, and the positive-electrode active material for a lithium secondary battery satisfies all of the following (i) to (iii): (i) in a cross section of the secondary particle, a ratio (B/A) of a minor axis length B of a figure surrounded by an outer edge of the cross section to a major axis length A of the figure is 0.75 or more and 1.0 or less, (ii) a proportion of a total area of the void exposed in the cross section to an area of the figure is 2.0% or more and 20% or less, and (iii) a proportion of an area of the void exposed in the cross section which is present in a center portion of the secondary particle to the total area of the void exposed in the cross section is 60% or more and 99% or less, where, in the figure, the major axis length is the longest diameter among diameters of the figure passing through a position of centroid of the figure, and wherein the center portion is a portion surrounded by a circle having a radius of r calculated by the following formula r = S / π 0.5 / 2, wherein the area of the figure is S and the position of centroid of the figure is the center of the circle, wherein a void fraction in the center portion of the secondary particle is 20% or more and 40% or less, and wherein a void fraction in a surface portion of the secondary particle is 0.10% or more and 3% or less when the surface portion is a portion excluding the center portion in the figure, wherein a composition formula of the lithium composite metal oxide is represented by Formula, Li[Li x (Ni( 1-y-z-w)Co y Mn z M w) 1-x]O 2... in Formula, 0.02 ≤x ≤0.04, 0.15 ≤ y≤ 0.4, 0.1 ≤ z≤0.3, 0 ≤ w ≤0.07, and M is one or more metals selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn; wherein the void fraction is determined as disclosed in paragraphs and of the description. a secondary particle in which a plurality of primary particles of a lithium composite metal oxide are aggregated, wherein the secondary particle has a void formed therein and a through-hole that connects the void to a surface of the secondary particle, and the positive-electrode active material for a lithium secondary battery satisfies all of the following (i) to (iii): (i) in a cross section of the secondary particle, a ratio (B/A) of a minor axis length B of a figure surrounded by an outer edge of the cross section to a major axis length A of the figure is 0.75 or more and 1.0 or less, (ii) a proportion of a total area of the void exposed in the cross section to an area of the figure is 2.0% or more and 20% or less, and (iii) a proportion of an area of the void exposed in the cross section which is present in a center portion of the secondary particle to the total area of the void exposed in the cross section is 60% or more and 99% or less, (i) in a cross section of the secondary particle, a ratio (B/A) of a minor axis length B of a figure surrounded by an outer edge of the cross section to a major axis length A of the figure is 0.75 or more and 1.0 or less, (ii) a proportion of a total area of the void exposed in the cross section to an area of the figure is 2.0% or more and 20% or less, and (iii) a proportion of an area of the void exposed in the cross section which is present in a center portion of the secondary particle to the total area of the void exposed in the cross section is 60% or more and 99% or less, where, in the figure, the major axis length is the longest diameter among diameters of the figure passing through a position of centroid of the figure, and wherein the center portion is a portion surrounded by a circle having a radius of r calculated by the following formula r = S / π 0.5 / 2, wherein the area of the figure is S and the position of centroid of the figure is the center of the circle, wherein a void fraction in the center portion of the secondary particle is 20% or more and 40% or less, and wherein a void fraction in a surface portion of the secondary particle is 0.10% or more and 3% or less when the surface portion is a portion excluding the center portion in the figure, wherein a composition formula of the lithium composite metal oxide is represented by Formula, Li[Li x (Ni( 1-y-z-w)Co y Mn z M w) 1-x]O 2... in Formula, 0.02 ≤x ≤0.04, 0.15 ≤ y≤ 0.4, 0.1 ≤ z≤0.3, 0 ≤ w ≤0.07, and M is one or more metals selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn; wherein the void fraction is determined as disclosed in paragraphs and of the description.