To provide possibility of installing vertical legs in such a way as adapting to the width of a block which may occur in three different values according to the standard specifications.

A supporting table is composed of a support plate 12 to be placed on the oversurface of a block, the first 14, second 16, and third vertical legs 18 arranged upright on the undersurface of the support plate 12 and positioned at the apices of an assumed triangle, and a column member 20 installed upright on the support plate 12. The spacing of the three legs 14, 16, and 18 is set so as to be capable of pinching any of the three sorts of blocks according to the minimum width (a), intermediate width (b), and maximum width (c) between all legs 14, 16, 18.