Valve device and assembly method of valve device

A valve device comprising:

• a housing having a cylindrical internal peripheral wall in which a columnar space is formed;
• a fluid introduction path being formed in the housing and communicating with the space in the internal peripheral wall;
• a fluid discharge path being formed in the housing and communicating with the space in the internal peripheral wall;
• a valve element having a communication path inside that brings the fluid introduction path and the fluid discharge path into communication with each other, and having, when seen along an axis center of the space in a state of being stored in the space, a major radial portion formed with a predetermined first internal radius associated with an internal radius of the internal peripheral wall of the housing, a minor radial portion formed with a second internal radius smaller than the first internal radius, and an intermediate portion that has an internal radius equal to or less than the first internal radius and equal to or more than the second internal radius and that is formed in such a way as to join the major radial portion and the minor radial portion together;
• a valve element rotation mechanism having the axis center as a rotation axis center and rotating the valve element inside the space;
• a seal member being provided on the internal peripheral wall and being able to contact the valve element rotating inside the space;
• and
• a shaft inserted in the space through a through-hole formed in the housing in such a way that the axis center of the valve element stored in the space in a state of being out of alignment with the rotation axis center is aligned with the rotation axis center in accordance with the seal member and an internal radius of the valve element.