In this paper, we propose a passive gravity vector control mechanism, which named "Mechanical Gravity Generator (MGG)." From development and geometry calculation of a link model with the MGG, it is clarified that our device has three advantages described below in comparison with conventional passive gravity compensation mechanisms and other handling mechanisms. (1) In all directions, it allows the passive stabilization of the links by setting parameters of MGG. (2) MGG increases the payload than conventional passive gravity compensation mechanisms when the link position is under the equilibrium positions. (3) The equilibrium positions of serial links with MGG can be designed independently for each link. In conclusion, the novel device enabled to get high power and easy posture control by the effect of generated virtual gravity.