Abstract: A valve assembly includes: a rotary gear being rotated about a vertical central axis that is a rotational axis by force from an outside, and having a non-circular insertion hole on the central axis; a cylindrical cam being able to move up and down while rotating integrally with the rotary gear with an upper end thereof inserted in the insertion hole, and having two or more inclined slide grooves on an outer side thereof; a poppet shaft disposed through the rotational axis of the cylindrical cam to be able to move up and down integrally with and rotate independently from the cylindrical cam; a valve seat coupled to a lower portion of the poppet shaft; a housing and a cover that surround the cylindrical cam; and two or more bearing unit each having a first side fixed to the housing and having second sides respectively inserted in the slide grooves.