The invention relates to an automatic marking vehicle for road traffic markings, and belongs to the field of road safety. An automatic marking device is arranged on the marking vehicle and comprises a man-machine interaction unit, an industrial personal computer, a vehicle positioning unit, stepping motors, an executing mechanism and a line width adjusting unit. The input ends of the industrial personal computer are connected with the man-machine interaction unit and the vehicle positioning unit respectively, and the output ends of the industrial personal computer are connected with stepping motor drivers and a spray switch trigger respectively. The number of the stepping motors is two, and the stepping motors are arranged on two driving wheels of the marking vehicle respectively and connected with the stepping motor drivers. The executing mechanism is fixed on a chassis of the marking vehicle, and connected with the spray switch trigger. Compared with the prior art, the automatic marking vehicle for the road traffic markings is provided, achieves the automatic marking function of the marking vehicle, and therefore achieves the aim of saving manpower.