Abstract: The present invention relates to a chassis frame assembly structure for an electrical vehicle, wherein welding assembly units are formed by attachment and welding at respective portions in each of which channel-shaped frames made of aluminum and each configured to have a hollow structure are coupled. The chassis frame assembly structure includes a plurality of fastening holes formed at proper interval close to the welding assembly unit of the chassis frames; reinforcement members each configured to have a channel shape, surround the periphery of the welding assembly unit of the chassis frame, and have a plurality of assembly holes, corresponding to the respective fastening holes, formed at proper intervals in one face of the reinforcement member; and fastening members assembled with the assembly holes and the fastening holes, wherein the reinforcement member is positioned at the outside of the chassis frame.