STABLE SUPPORT MECHANISM, AND POSTURE TRANSITION ASSIST APPARATUS, CHAIR, AND MOBILE APPARATUS THAT USE THE SAME

To stably support a user before and after posture transition between a standing position and a sitting position by suppressing forward and backward movement of a position of the center of gravity of a user without power supply with a simple configuration. A stable support mechanism includes a base, a support structure mounted on the base, the support structure being configured to be capable of translational movement along a first axis in a plane horizontal to the base, the support structure being configured to be capable of changing a posture between a first position and a second position in a plane perpendicular to the base, and a link having a fixed length, one end of the link being connected to the base, the other end of the link being connected to the support structure, the link being configured to guide the support structure in a direction along the first axis along with changing the posture of the support structure.