This paper describes a biomechanical evaluation of tasks using wheeled lifting devices with a universal sling. The tasks were partitioned into eight phases: sling application, strap attachment, patient elevation, patient transport, patient lowering, strap detachment, sling removal from the legs, and sling removal from the back. Each task was measured using a Vicon system with seven cameras, a force plate, and an EMG measurement device. Three-dimensional moment at the lower back was calculated from the movement and the ground reaction force through a body segment model. The results of the EMG showed that sling application, patient transport, and sling removal from the legs required large muscle activities. Sling application and sling removal from the legs required a large peak moment and large average moment. Sling application also indicated long duration. Moments caused by an upper body weight were then calculated. As a result, these two phases were shown to generate a large moment caused by the stooped posture of the caregiver, who was bending forward during these phases. Patient transport required large twisting moments for turning of the lift to the right and left. These moments were related to a moment about a center of pressure of ground reaction force. Angles of caregiver's trunk inclination were measured during sling application and sling removal from the legs. A belt sling and a universal sling were selected and bed heights of 0.55, 0.65, and 0.73 meter, and wheelchair heights of 0.38 and 0.43 meter were set as measurement conditions. The moment index calculated from the angles showed no significant difference between the two slings in the sling application task. A lower back load index, which was the moment index multiplied by duration, however, indicated that the belt sling required significantly smaller lower back loads than did the universal sling. On the other hand, in sling removal from the legs, the moment index and lower back loads index showed that the belt sling required significantly smaller lower back loads than did the universal sling. In addition, it was indicated that a higher bed required smaller lower back loads on caregivers. There was no relationship between wheelchair height and lower back loads. Subsequently, ground reaction moments about the center of pressure of ground reaction force were measured during turning of the lifting device toward the right. There were two methods: turning it centered around the caregiver (method A), and turning the lifting device centered around itself (method B). Method B required smaller peak lower back loads than method A. Large peak moments were indicated in method B, however, when the subjects did not step in the direction of rotation. These results showed the significance of evaluating assistive devices using biomechanical methods. They will likely improve the education of caregivers and the development of new devices.