A variable flow rate valve mechanism includes a valve including a valve body and a valve shaft projecting from the valve body, a lock member fixed to the valve shaft at a position axially spaced from the valve body, an attachment member disposed between the valve body and the lock member and holding the valve together with the lock member, and a spring washer disposed between the lock member and the attachment member or between the attachment member and the valve body, and contacting the lock member or the valve body and the attachment member to impart an elastic force to the attachment member. A first member or a second member has an inner face, the inner face facing radially inward and facing an outer peripheral portion of the spring washer.