The invention discloses a welding and fixing device for a sheet metal part. The device comprises a base, a welding support plate, a pressing plate and a depression bar, wherein the welding support plate is placed on the base, a channel is formed in the middle of the welding support plate, and the pressing plate is used for fixing the sheet metal part on the welding support plate; the two ends of the depression bar are provided with cylindrical pressing legs, and slotted holes matched with the diameters of the pressing legs are formed in the four corners of the base so that the pressing legs can be placed in the slotted holes. According to the welding and fixing device provided by the invention, the pressing plate can be designed to horizontally move in the channel, the welding and fixing device can be fixedly adjusted according to the length of the sheet metal part, therefore the welding and fixing device is applicable to welding the sheet metal parts of various length specifications; furthermore, by increasing the decompression bars with the pressing legs, spring extended buttons on the pressing legs are matched with slots in the slotted holes, therefore the welding and fixing device is applicable to welding the sheet metal parts of various thickness specifications; in addition, the welding and fixing device is wide in range of application and strong in universality, and finished products can be greatly saved in the product processing process.