A valve disk of a double eccentric butterfly valve having boss sections (3, 4) for accommodating a stem (8) and rib sections (6, 7) each extending toward outer edge portions of the valve disk in a direction intersecting a stem (8) from the boss sections are provided on a surface on one side of a disc (2), and each of the ribs respectively excluding the boss sections is provided such that a height from a surface (2a) of the disc on the side on which a distance to an end on the edge portion side of the valve disk is longer than that on the side on which a distance to an end on the edge portion side of the valve disk is short when the heights are respectively compared at positions spaced an equal distance apart from a stem center axis (20), and the butterfly valve.