The invention discloses a CAD data processing device and a CAD data processing method. Specifically, the invention relates to the field of computers, the device comprises a graph scanning module, a graph partitioning module, a graph extraction module, a graph locking module, a graph merging module and a graph unlocking module, the graphic scanning module comprises a graphic scanning unit; the graph partitioning module comprises a graph partitioning unit; wherein the graph extraction module comprises a graph layer new establishment unit and a graph copy unit, the graph locking module comprises a graph locking unit, the graph merging module comprises a graph merging unit and a graph layer deletion unit, and the graph unlocking module comprises a graph unlocking unit and a graph storage unit. A graph is scanned through the graph scanning module, partition is conducted through the graph partition module, a graph area needing to be modified is extracted through the graph extraction module, an area not needing to be modified is locked through the graph locking module, and the safety of the system is higher on the whole.