This paper proposes a standing-up motion support system for complete paraplegic patients who cannot stand up by himself/herself due to a spinal cord injury. The standing-up motion is the first step for us to move somewhere inside and outside in our daily life. Therefore, the standing-up motion support is indispensable for patients to promote his/her independent life. The proposed support system using an exoskeletal assistive system ldquoRobot Suit HALrdquo supports the wearer's weight during his/her standing-up motion so that he/she can stand up without any physical efforts. Besides, the support system controls the patient's posture for his/her stability to avoid falling down during the standing-up motion. The system also estimates his/her intention to stand up based on a preliminary motion of his/her upper body. The patient therefore starts the standing-up without any operations, just by bending his/her upper body forward as the preliminary motion. First, the system performance with respect to the weight-bearing and the balance control was confirmed through the experiment, by supporting a mannequin's standing-up. Then, the proposed system including the intention estimation algorithm was provided for a complete paraplegic patient in order to verify the performance of the total system. In consequence, we confirmed that the proposed system safely supported his standing-up according to his intention.