The invention discloses a double-face groove forming method and device. The method comprises the steps that two gas cutting devices are movably mounted on tracks, wherein a flame jetting gun head of one of the gas cutting devices is arranged inwards in an inclined manner, and a flame jetting gun head of the other gas cutting device is arranged outwards in an inclined manner; and the flame jetting gun heads jet flames, the two gas cutting devices are controlled to move on the tracks, and cutting is conducted on a side edge of a panel so that a double-face groove can be formed. According to the double-face groove forming method and device, the two gas cutting devices are movably mounted on the tracks, and cutting of double faces of the groove can be conducted at the same time; cutting efficiency is high; in addition, the formation of the double-face groove is conducted at the same time; quality and precision of welding seams can be guaranteed; and manpower and material resources are saved.