A welding wire feeding device includes a base, a fixing post, a pressing member, a motor, and a conveying mechanism. The pressing member is pivotally connected with a driven wheel. A tension spring is provided between the fixing post and the pressing member. A shaft portion of the motor is pivotally connected with a driving wheel. The conveying mechanism is coupled to the base and has an air hole. The base is formed with a first passage and a second passage connected with a gas cylinder. The length of the conveying tube of the conveying mechanism can be adjusted by pressing. A wire is sandwiched between the driving wheel and the driven wheel through the tension spring. The motor drives the driving wheel to rotate the driven wheel so as to continuously convey the wire; meanwhile, the inert gas can be sent out through the second passage and the conveying mechanism to prevent a workpiece from being oxidized.