A wheelchair transfer device is configured for moving an invalid patient from a flat surface to a seated position for transport in the seated position on the transfer device. The transfer device includes a rolling base supported by casters and convertible low profile rollers that are configured to fit under the base of a hospital bed and convert to a larger diameter wheel without altering the height of the transfer device. The transfer device includes a leg portion, a torso portion and a seat portion configured to be coplanar for adaptation to a hospital bed, so that an invalid patient can, with assistance, roll onto the device. The seat portion can then be raised against the patient's buttocks, generally perpendicular to the leg and torso portions, and the whole assembly can then be rotated to a vertical position, with the seat portion supporting the weight of the patient.