A method for producing megakaryocytes and/or platelets, the method comprising: separating hematopoietic progenitor cells and cells that form a septum of a net-like structure produced by pluripotent stem cells, in the presence of a compound represented by formula (I), a tautomer of the compound, a prodrug, a pharmaceutically acceptable salt of these, or a solvate of these compounds;?culturing the resulting hematopoietic progenitor cells in vitro;?and differentiating the same into megakaryocytes and/or platelets.