Side support folding device under bedstead

The utility model discloses a lateral bracket folding device arranged on the bottom of a bed frame, which can decrease the volume of a lateral bracket after folded. The utility model comprises two lateral brackets, two sliding sleeves and a pivoted joint sleeve, wherein each sliding sleeve is protruded with an upper and a lower lugs which are corresponding to each other, each lug can be pivoted with one end of the lateral bracket, and each sliding sleeve is provided with a sleeve joint groove used for pivotally sheathing on a master bracket of the bed frame; the pivoted joint sleeve is provided with a pivoted joint groove used for pivoting with the other ends of the two lateral brackets. The folding of the lateral brackets pivoted in the pivoted joint sleeve cooperates with the sliding sleeves to rotate on the master bracket, so that each lateral bracket can fold to the minimal volume, which is convenient for storage.