With the increase of the elderly population, the assistive technology for their walking has been needed. Although some walking support devices have shown positive effects, they still have problems for easy to suit it by oneself. In this study, it is aimed to develop a new walking assist device which can be used for hemiplegia and has feasibility of adjustment for assisting power without any actuators. As a first step, a motion transmission mechanism between lower limbs has been proposed and implemented as a prototype. The basic function and effects of motion transmission from unaffected side to affected side without any control are verified through the experiments using the prototype with a simple biped leg model. In addition, it is confirmed that the variation of attachment positions of transmission mechanism on the bipedal model offers the adjustability of transmitted torque. And, it is verified that the attachment of the proposed mechanism on the biped model has the positive effects on the periodicity and stability of the gait motion. As a future work, it is needed to redesign a motion transmission mechanism which suits for the actual human leg and its motion with the safety and the consideration for the load to the unaffected limb.