Therapeutic method for blood coagulation disorder

Disclosed is a therapeutic agent for blood coagulation disorder comprising, as an active ingredient, a lentivirus vector having a blood coagulation factor gene operably linked to a promoter capable of inducing the expression of the gene in a platelet-specific manner. By using a gene encoding factor VIII or factor IX in place of the blood coagulation factor gene, a therapeutic agent for hemophilia A or B can be provided. Blood coagulation disorder can be treated by gene therapy by infecting a hematopoietic stem cell or the like with the therapeutic agent.