A method for producing megakaryocytes and/or platelets, comprising (i) forming hematopoietic progenitor cells ex vivo in a sac-like structure by differentiating human induced pluripotent stem (iPS) cells, wherein the sac-like structure is a three-dimensional saccular structure containing hematopoietic progenitor cells inside; and (ii) culturing the hematopoietic progenitor cells separated from the septal cells of the sac-like structure ex vivo in the presence of a compound represented by the formula, a tautomer, prodrug or pharmaceutically acceptable salt of the compound or a solvate thereof, for differentiating the hematopoietic progenitor cells into megakaryocytes and/or platelets: wherein W is a substituent represented by the formula (Ia): R 1 is a methyl group, each of R 2, R 3, R 4 and R 6 is a hydrogen atom, n is an integer of 1 or 2, R 5 is a phenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 3-pyridazinyl group, a 4-pyridazinyl group, a 2-pyrimidinyl group, a 4-pyrimidinyl group, a 5-pyrimidinyl group, or a 2-pyrazinyl group which may be substituted with one or more substituents independently represented by V 1, provided that when n is 2, R 5 is not an unsubstituted pyridyl group, R 7 is a phenyl group which may be substituted with one or more substituents selected from methyl groups, t-butyl groups, halogen atoms, methoxy groups, trifluoromethyl groups and trifluoromethoxy groups, or is a substituent represented by any one of the formulae to: Ar 1 is represented by the formula: X is -OH, each of Y and Z is independently an oxygen atom or a sulfur atom, and V 1 is represented by any one of the formulae to (XXII): (i) forming hematopoietic progenitor cells ex vivo in a sac-like structure by differentiating human induced pluripotent stem (iPS) cells, wherein the sac-like structure is a three-dimensional saccular structure containing hematopoietic progenitor cells inside; and (ii) culturing the hematopoietic progenitor cells separated from the septal cells of the sac-like structure ex vivo in the presence of a compound represented by the formula, a tautomer, prodrug or pharmaceutically acceptable salt of the compound or a solvate thereof, for differentiating the hematopoietic progenitor cells into megakaryocytes and/or platelets: wherein W is a substituent represented by the formula (Ia): R 1 is a methyl group, each of R 2, R 3, R 4 and R 6 is a hydrogen atom, n is an integer of 1 or 2, R 5 is a phenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 3-pyridazinyl group, a 4-pyridazinyl group, a 2-pyrimidinyl group, a 4-pyrimidinyl group, a 5-pyrimidinyl group, or a 2-pyrazinyl group which may be substituted with one or more substituents independently represented by V 1, provided that when n is 2, R 5 is not an unsubstituted pyridyl group, R 7 is a phenyl group which may be substituted with one or more substituents selected from methyl groups, t-butyl groups, halogen atoms, methoxy groups, trifluoromethyl groups and trifluoromethoxy groups, or is a substituent represented by any one of the formulae to: Ar 1 is represented by the formula: X is -OH, each of Y and Z is independently an oxygen atom or a sulfur atom, and V 1 is represented by any one of the formulae to (XXII): R 1 is a methyl group, each of R 2, R 3, R 4 and R 6 is a hydrogen atom, n is an integer of 1 or 2, R 5 is a phenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 3-pyridazinyl group, a 4-pyridazinyl group, a 2-pyrimidinyl group, a 4-pyrimidinyl group, a 5-pyrimidinyl group, or a 2-pyrazinyl group which may be substituted with one or more substituents independently represented by V 1, provided that when n is 2, R 5 is not an unsubstituted pyridyl group, R 7 is a phenyl group which may be substituted with one or more substituents selected from methyl groups, t-butyl groups, halogen atoms, methoxy groups, trifluoromethyl groups and trifluoromethoxy groups, or is a substituent represented by any one of the formulae to: Ar 1 is represented by the formula: X is -OH, each of Y and Z is independently an oxygen atom or a sulfur atom, and V 1 is represented by any one of the formulae to (XXII):