A potassium channel opener including a compound (e.g., pimaric acid) represented by the formula [I]:wherein R1, R2, R3, R4, R5, R6 and R7 are each independently hydrogen, alkyl, alkenyl, halogen, hydroxy, halogenated alkyl, hydroxyalkyl, aminoalkyl, alkoxy, aryl, heteroaryl, acyl, carboxyl, alkoxycarbonyl, hydroxamate, sulfo, carbamoyl, sulfonamide, aldehyde, or nitrile; or R4 and R5 may be bonded to each other to form a ring; or R6 and R7 may be bonded to each other to form a ring; and all of three bonds represented by are single bonds, or one of the three bonds is double bond and the other bonds are single bonds, or a physiologically acceptable salt thereof as an effective ingredient.