The invention provides a welding structure of a circuit board, wherein a welding wire passes through a first through hole on a first welding point of a first circuit board and a second through hole on a second welding point of a second circuit board to connect the first welding point of the first circuit board and the second welding point of the second circuit board, wherein the welding wire is in a bending shape to avoid the condition that the welding wire separates from the first through hole and the second through hole. By using the welding structure of the circuit board, two tail end parts of the welding wire can be welded with the corresponding welding points to switch on the first circuit board and the second circuit board. Because the welding wire can assuredly pass through the first circuit board and the second circuit board, the structure intensity of the welding structure of the circuit board can be effectively increased. Besides, the welding method corresponding to the structure is utilized, the steps are simple and easy to operate, and various worse conditions caused by poor technique of an operator can be reduced.