The invention relates to a welding fume purifying device capable of improving the working efficiency of workers and good in purifying effect. The welding fume purifying device comprises a main body, trundles, an air suction arm and an air suction cover. The main body further comprises a bottom adjusting mechanism and a side face adjusting mechanism. The bottom adjusting mechanism comprises a rotating assembly and a supporting assembly. The side face adjusting mechanism comprises a fixing ring, a lifting assembly and a horizontal movement assembly. According to the welding fume purifying device capable of improving the working efficiency of workers and good in purifying effect, by means of cooperated work of the bottom adjusting mechanism and the side face adjusting mechanism, the position of the air suction cover is automatically adjusted, the air suction cover sucks fume along with movement of a fume source, convenience is brought to welding work of workers, and the working efficiency of workers is improved; and meanwhile, the fume suction cover can be precisely and automatically adjusted to the fume source to suck fume to the greatest degree, and the purifying effect is enhanced.