The invention discloses a lace weaving device in a shuttleless loom. The lace weaving device comprises dobby chain sheets. The outer curve of each dobby chain sheet is matched with the outer circle of a bearing on a blade group to form a cam-driving rolling shaft structure. Each blade group drives and is connected with one end of a connecting rod, wherein the other end of the connecting rod is connected with a thin guide rod through a rotating pin, the other end of the thin guide rod is fixedly connected into a connecting block, the connecting block transmits torque to an aluminum connecting piece in a coaxial mode, a steel wire rod is eccentrically connected to the aluminum connecting piece to form a crank connecting rod mechanism, and the farthest track position of the other end of the steel wire rod is located at a weaving opening. When weft needles move to overlock needles, the other ends of the steel wire rods arrive at the farthest track positions; meanwhile, the overlock needles move downwards, hooks press weft threads, crochet needles hook overlock threads, the weft needles retreat, and the overlock threads form a circle. The lace weaving device achieves the lace weaving function on the shuttleless loom, and is reliable in structure and low in refitting cost.