Fully-hidden furniture plate body connecting piece and connecting method

The invention discloses a fully-hidden furniture plate body connecting piece and a connecting method, and belongs to the technical field of furniture plate body connecting pieces. The fully-hidden furniture plate body connecting piece comprises a fixed box, a box cover is arranged at the upper end of the fixed box, and a rotating shaft is arranged at the bottom of the interior of the fixed box. A second transmission bevel gear connected with the driving bevel gear in a meshed mode rotates, the second transmission bevel gear drives a transmission rod to rotate, a first transmission bevel gear at the other end of the transmission rod rotates, the first transmission bevel gear drives a driven bevel gear to rotate so that a double-end lead screw can rotate, and a sliding block connected with the double-end lead screw moves to drive a fixing block to be stored in a fixing box. One end of the fixing box is inserted into a groove of a fully-hidden furniture plate body, the other end of the fixing box is inserted int