A thrust generating device (10) immersed in water and generating thrust by expelling water, wherein a rotor body (43) comprises: a first member (48) having a side surface and an outer peripheral surface which face a first water-lubricated bearing (40); a second member (49) having a side surface and an outer peripheral surface which face a second water-lubricated bearing (41); and a third member (50) having a support surface making contact with the inner peripheral surface of a rotor core (44), and the first to third members (48-50) are removably affixed to each other.