A cell structure for use in a method of brain damage treatment which contains biocompatible macromolecular blocks and at least one kind of cell and in which a plurality of the biocompatible macromolecular blocks are disposed in gaps between a plurality of the cells, wherein the tap density of the biocompatible macromolecular block is 10 mg/cm 3 to 500 mg/cm 3 or wherein a value obtained as an average value by measuring a plurality of biocompatible macromolecular blocks which are greater than or equal to 10 biocompatible macromolecular blocks by dividing the square root of the cross-sectional area in a two-dimensional cross-sectional image of the biocompatible macromolecular block by the peripheral length is 0.01 to 0.13, wherein the "square root of cross-sectional area / peripheral length" of a biocompatible macromolecular block in the two-dimensional cross-sectional image are obtained by preparing a sliced sample of the cross-sectional structure of the biocompatible macromolecular block and observing the cross-sectional structure, wherein the cells include at least mesenchymal stem cells and/or bone marrow cells, wherein the biocompatible macromolecular block consists of a recombinant peptide, wherein the recombinant peptide is a biocompatible peptide, and wherein the biocompatible macromolecular block is a biocompatible macromolecular block produced through a method including the step (a) of freezing the solution of the biocompatible macromolecules through the freezing treatment in which the highest internal liquid temperature, which is a liquid temperature in a portion having the highest liquid temperature within the solution, becomes lower than or equal to a temperature which is 3°C lower than a melting point of a solvent in an unfrozen state, the step (b) of freeze-drying the frozen biocompatible macromolecules which have been obtained in the step (a), and a step (c) of grinding a porous body which has been obtained in the step (b), wherein the number of cells to be administered per administration is 1.0 x 10 4 to 5.0 x 10 7 pieces/kg body weight. wherein a value obtained as an average value by measuring a plurality of biocompatible macromolecular blocks which are greater than or equal to 10 biocompatible macromolecular blocks by dividing the square root of the cross-sectional area in a two-dimensional cross-sectional image of the biocompatible macromolecular block by the peripheral length is 0.01 to 0.13, wherein the "square root of cross-sectional area / peripheral length" of a biocompatible macromolecular block in the two-dimensional cross-sectional image are obtained by preparing a sliced sample of the cross-sectional structure of the biocompatible macromolecular block and observing the cross-sectional structure, wherein the cells include at least mesenchymal stem cells and/or bone marrow cells, wherein the biocompatible macromolecular block consists of a recombinant peptide, wherein the recombinant peptide is a biocompatible peptide, and wherein the biocompatible macromolecular block is a biocompatible macromolecular block produced through a method including the step (a) of freezing the solution of the biocompatible macromolecules through the freezing treatment in which the highest internal liquid temperature, which is a liquid temperature in a portion having the highest liquid temperature within the solution, becomes lower than or equal to a temperature which is 3°C lower than a melting point of a solvent in an unfrozen state, the step (b) of freeze-drying the frozen biocompatible macromolecules which have been obtained in the step (a), and a step (c) of grinding a porous body which has been obtained in the step (b), wherein the number of cells to be administered per administration is 1.0 x 10 4 to 5.0 x 10 7 pieces/kg body weight.