PURPOSE: To stably support an object to be supported, by supporting the object in such a way that the object is put between two movable rotary supporting shafts closely to a fixed rotary supporting shaft.

CONSTITUTION: Two fixed rotary supporting shafts P1 and P2 are arranged in parallel with a moving body B and two movable rotary supporting shafts Q1 and Q2 are provided in parallel with each other at positions lower than the supporting shafts P1 and P2 in elevation. Objects to be supported, such as an antenna AT, transmitter-receiver, etc., are supported by the supporting shafts Q1 and Q2. When the center of gravity of the whole objects to be supported is brought nearer to the intersection point of segments P1Q1 and P2Q2 as much as possible, the axis EL-EL of the antenna AT is supported almost horizontally, even when an impact force acts on the objects to be supported from the outside.