The wireless sensor network (WSN) based on ad hoc network is applied to vehicle parking guide system without parking guide man at area or building with large scale of parking lots. The optimum number of cluster heads was derived for getting the minimum power consumption as well as time delay. Through the theoretical analysis of power consumption and time delay with the number of cluster heads in wireless sensor network, it was found that there exists the minimum point in the variation of power consumption and time delay according to the number of cluster heads.