The present invention provides a thread groove pump mechanism which suppresses a backflow of the gas in the thread groove pump mechanism and reduces the pressure difference in the pump radial direction near the outlet of the thread groove pump mechanism to thereby improve the exhaust performance and the compression performance. The present invention also provides a vacuum pump including the thread groove pump mechanism, and a rotor, an outer circumference side stator, and an inner circumference side stator used in the thread groove pump mechanism. A thread groove pump mechanism includes an exhaust-performance improving means in an outer-circumference-side thread groove portion engraved on an opposite surface of an outer circumference side stator opposed to a rotor cylinder portion and an inner-circumference-side thread groove portion engraved on an opposite surface of an inner circumference side stator opposed to the rotor cylinder portion.