Abstract: Shaking area of the shake table of a motor-driven shaker used for shake culture and the like can be enlarged or reduced by adjusting the eccentricities of plural support legs with respect to corresponding shafts. According to the present invention, mere adjustment of the eccentricity of a central support leg results in automatical eccentricity adjustment of the other peripheral support legs each having a magnet secured thereto which slidably engages with a free disc per se rotatable with its shaft, since the magnet is driven while generating a circle on the free disc following an eccentrical movement of the central support leg and such circle ought to coincide of itself with a concentrical circle with respect to the shaft.