To dispense with a coating processing and to reduce a cost by assembling a sealing member sliding with an inner wall of a housing on at least one side of a tooth end part and an end face part of each rotor, in a machinery having a pair of rotors stored within the housing and engaged each other.

In a pair of rotors 3, 5 molded into the same shape as a cocoon shape, both ends of each shafts 17, 19 are supported by each bearing. In a core part of each tooth part of each rotor 3, 5, a cylindrical mass removing hole 33 passing through in an axial direction is formed and moment of inertia is reduced. In this case, each groove is formed over the entire length of the axial direction at a tip part of each tooth part and each sealing member 35 made of a low frictional material is fitted into each of the grooves. As a result, each sealing member 35 is brought into sliding contact with an inner wall surface of a housing 7 and each tooth bottom surface of opposite side rotors 3, 5, respectively, according to synchronous rotation of each rotor 3, 5 and leakage of fluid to a suction side is surely prevented.