The present invention relates to a butterfly valve having a quadruple eccentric structure which can maintain excellent airtightness in a high-temperature high-pressure condition and a bidirectional fluid flow condition. The butterfly valve has a valve disk provided with an inclined surface formed along an edge in a valve body having a hollow space and installed to be rotated by a valve shaft. A seat unit is separated from an inter-surface center line of the valve body to one side in the longitudinal direction of the valve body to protrude from the inner circumferential surface of the valve body. The valve shaft is separated from a flow path center line of the valve body to one side in the lateral direction of the valve body to be installed. The valve disk is installed to be inclined by rotating a reference axis of a conic angle formed by the inclined surface of the edge by a prescribed angle with respect to the flow path center line and rotating a center line on a longitudinal section by a prescribed angle with respect to the inter-surface center line. The cross section of an elliptic cone at the center line on the longitudinal section parallel with the inter-surface center line is formed in a circular shape.
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