A vacuum pump has, in at least either a stator disc to be disposed or a rotating disc to be disposed, a Siegbahn type molecular pump portion in which a spiral-shaped groove with a ridge portion and a root portion is engraved (disposed), and is structured to ensure high conductance at a returning flow channel formed at the outer periphery (outside) of the Siegbahn type molecular pump portion. This structure is created by a communicating portion (a groove portion, a slit) formed on each rotating disc, or an oblique plate disposed on the stator disc and the communicating portion formed on the rotating disc. The “communicating portion,” “groove portion,” and “slit” are configured to have “concave” shapes, a concave portion is provided by engraving a groove radially inward from an outer diameter portion (toward a side of a shaft of the vacuum pump) in the rotating disc (or stator disc).