This valve device includes a body having passages and valve shaft holes, a valve shaft passed through the valve shaft holes in a rotatable manner, and butterfly valves. The butterfly valves include first contour parts and second contour parts forming outer contour parts that are smaller than the first contour parts. The first and second contour parts are fixed to the valve shaft in order to close off the passages at positions set apart from the valve shaft holes toward the downstream side (upstream side) of the passages, and are disposed flanking a straight line parallel to the valve shaft to form prescribed outer contour parts. The body includes first seal parts with which the first contour parts are brought into contact and second seal parts with which the second contour parts are brought into contact within the passages. Fluid leakage in a closed state can thereby be reliably prevented.