To enable use both for very active and ordinary sports by stably supporting a waist against vertical intense impacts while securing certain degree of freedom in horizontally twisting of the waist.

This support resin plate is provided with holes 2, 3, and 3' at a segment of a part along a portion contacting a lumbar and at segments of parts 11 and 11' contacting a portion slightly biased to the rear center of right and left broadest muscles of back. The holes 2, 3 and 3' are 10-60% in the proportion of area and the hole 2 is so shaped to be fitted into a protruded part for fitting a protective pad. Notches 30-33 and 30'-33' are arranged between the part 10 and the part 11, between parts 11 and 11' and parts 12 and 12' contacting the part biased to sides out of right and left broadest muscles of back. this plate is provided with hole 4 and 4' for mounting that can be engaged with protrusions of an elastic bone.