The invention discloses a device for automatically marking defective welding spots of a circuit board. The device comprises a circuit board delivering guide rail component, a circuit board delivering push frame component, an XY coordinate positioning and marking mechanism and a control system. The circuit board delivering guide rail component is used for placing the circuit board and allowing the same to linearly move forwardly in a slide manner. The circuit board delivering push frame component is used for pushing and delivering the circuit board. The XY coordinate positioning and marking mechanism is used for adjusting XY coordinate positions for dotting. The control system is used for controlling the circuit board delivering guide rail component, the circuit board delivering push frame component and the XY coordinate positioning and marking mechanism to operate. The circuit board delivering guide rail component, the circuit board delivering push frame component and the XY coordinate positioning and marking mechanism are respectively connected with the control system. The device using the open structure is simple in structure and convenient to maintain, human participation degree during production is reduced, manual mistakes can be avoided, production stability and accuracy can be increased, efficiency and quality of enterprise production are increased, and automatic production and informatization management of enterprises are promoted.