A vehicle occupant information acquisition device includes a microcomputer, an acquisition unit and an alert unit. The microcomputer controls the vehicle to switch between an autonomous driving mode and a manual driving mode. The acquisition unit acquires, from vehicle occupants riding in the vehicle, information relating to driving suitability of the vehicle occupants. In a case in which the microcomputer is switching the vehicle from the autonomous driving mode to the manual driving mode, the microcomputer causes the alert unit to alert one of the vehicle occupants who is determined to be suitable to drive the vehicle based on the information acquired by the acquisition unit that he/she has been selected as the driver of the vehicle.