A multi-inlet vacuum pump includes a first pump device (10) including a first rotor element (18) with a plurality of first rotor disks (20) serially arranged in the conveying direction (36), and a second pump device (12) including a further rotor element (26) with a plurality of second rotor disks (28) serially arranged in the conveying direction (36). A diameter of the second rotor disks (28) is at least partially larger than a diameter of the first rotor disks (20). A main inlet (32) sucks in a first fluid stream (34) with the first pump device (10). The first fluid stream (34) is conveyed in the direction of the further pump device (12). An intermediate inlet (38) sucks in a second fluid stream (40) with the second pump device (12). The second fluid stream (40) is conveyed in the direction of a pump outlet. A process of merging the two fluid streams (34,40) will occur within the second pump device (12), preferably between two adjacent second rotor disks (28) of the second pump device (12).