Describes a 3D biped robot where each leg is composed of a 6 DOF parallel mechanism. The proposed mechanism is suited to walking, and the total weight of each leg is expected to be lighter than a serial linked biped robot. This is one of the remarkable features of the proposed mechanism. One side leg consists of three linked arms. Each arm has two active and four passive joints, and is placed in the same direction. There are two kinds of arms where positions of the active joints are different. Thus, the robot can move without interference of each arm. In the paper, theoretical analysis of the biped robot motion with parallel mechanism is shown. Furthermore a 3D dynamic simulator is developed to implement several simulations. To confirm the feasibility of the proposed mechanism, the walking motion is tested by the developed simulator.