A method of making a composite board and a product made thereby are disclosed. The method includes a lining forming step, a fiber pipe rolling step, a fiber pipe mounting step, a fiber material covering step, and a board body forming step. The product includes a lining acting as a board body, a plurality of long slots formed on the lining, a fiber pipe placed in each of long slots, a foam material mounted in each of fiber pipes, and a fiber material covering an external periphery of the lining. The fiber materials and the fiber pipes are melted and combined together by heat, thereby shortening the operating time. The fiber pipe becomes a reinforcement support structure to increase a structural strength of the composite board, thereby producing a finished product with a light weight and a strong structure.