Disclosed is a low-cost composite-type vacuum pump having a strength capable of withstanding high loads and using a cylindrical rotor formed from a fiber-reinforced plastic material. Having a turbo-molecular pump section (14) and a thread groove pump section (15), the composite vacuum pump is formed by press-fitting a joint portion (20a) of a rotor (17) of the turbo-molecular pump section (14) into the upper end section of a cylindrical rotor (21) formed from the fiber-reinforced plastic material of the thread groove pump section (15). The joint portion (20a) of the rotor (17) is formed on the lower end side of the rotor (17) integrally with said rotor (17) and in the shape of a cylinder with an L shaped cross section, and is provided with: a contact portion (28) having an outer diameter enable press-fitting into the inner peripheral face of the cylindrical rotor (21); and a small-diameter section (29) positioned above said contact portion (28) and, having an outer diameter smaller than the inner diameter of the aforementioned cylindrical rotor (21), capable of being placed inside the cylindrical rotor (21) away from the inner peripheral face of the cylinder rotor (21).