A modular circuit board structure for a large current area includes a circuit board having an electric conducting circuit and at least one large current area, and a conducting plate device having conducting plates installed onto the circuit board according to the shape of the large current area. When electronic components are inserted onto the circuit board by a surface mount technology, the conducting plates are attached onto the large current area to form a solder area portion on the conducting plates for allowing a large current to pass through, so as to provide a flexible combination function for the large current area of the circuit board and simplify the stamping molds of different shapes. The invention can avoid a waste of copper plates, assure the reliability, quality and safety of the circuit board, and enhance the cost effectiveness of the manufacture and the competitiveness of the product.