PURPOSE: To prevent adsorption due to a surface tension caused by water on surfaces of a protruded element and a stopper by constructing the surface of bot or either of the rotruded element of a suspension frame and the stopper of a non-metal material hard to moisten.

CONSTITUTION: A suspension frame 3 having a horizontal compensation prism 8 fastened thereon is suspended with four hanging wires 2 on support bases 1 and 1 fixed on a surveying appratus in such a manner as to be free to oscillate. Projected element 15 is provided midway on the stay 6 of suspension frame 3 and stoppers 16 and 16 are provided projected on the undersurface of one support base 1 to regulate the oscillation of the suspension frame 3 exceeding a specified angle. The protruded element 15 and the stoppers 16 and 16 are made of a relatively hard plant fiber such as bamboo and wood, a porous ceramic, a hydroscopic synthetic resin or the like. This eliminates bearing magnetism and does not allow any water attached to the surface to be infiltrated inside, thereby protecting the apparatus from magnetic action and surface tension of water.