Balance has properties of steadiness, symmetry and dynamic stability and plays an important role in relation to rehabilitation of fallen or hemiparalyzed patients. In this study, degrees of muscle activities of lower limb muscles like tibialis anterior, gastrocnemius, rectus femoris and biceps femoris were analyzed in relation to balance according to direction of shift in balance of human body by making use of self-developed balance board. Power spectral density value was used to compare the relative inter-muscular muscle activities according to inclination in 4 directions of front, back, left and right, as well as to compare degrees of muscle activity at front and back directions according to flexion and extension of knee joint. Results showed much muscle activities for tibialis anterior and rectus femoris of the opposite leg when leaning to the left or right while much muscle activities were present for gastrocnemius and tibialis anterior when leaning to the front and back, respectively.