To provide a compound which has an anticoagulation action based upon inhibition of activated blood coagulation factor X and is useful as an anticoagulant or an agent for prevention and treatment of diseases caused by thrombus or embolus. A diazepan derivative such as 4-[(3-carbamimidoylphenylamino)methyl]-3-[4-(4-methyl-1,4-diazepan-1-yl)b- enzoylamino]benzoic acid and 3-hydroxy-4'-methoxy-2-{[4-(4-methyl-1,4-diazepan-1-yl)benzoyl]amino}benz- anilide or a salt thereof is an effective ingredient.