A medical arm assembly according to embodiments disclosed includes: a remote joint where a remote point spaced forward from a reference point is located; a positioning arm section configured to support the remote joint, move the remote joint that a relative position of the remote point with respect to the reference point is changed in forward-and-rearward direction and upward-and-downward direction, and fix the relative position of the remote point with respect to the reference point; an operating arm section connected to the remote joint and configured to fix a surgery tool, rotate the surgery tool about a remote-rotation axis through the remote point in left-and-right direction, and move the surgery tool in a direction perpendicular to the remote rotation axis and through the remote point; and an arm supporting section where the positioning arm section and the operating arm section are supported by connecting and the reference point is located.