The present invention provides a single-surface welding device. The single-surface welding device of the invention is provided with the following components: a retaining plate device with a retaining plate copperplate, and a welding machine which welds along a welding line direction. The single-surface welding device is provided with a recovery and scattering trolley which scatters and recovers welding flux for an upper surface of the retaining plate copperplate of the retaining plate device. The recovery and scattering trolley moves based through the traction based on a driving mechanism of a chain, and is supported by a guiding mechanism which is provided at an outer side surface of a supporting structure. The chain is connected with the recovery and scattering trolley through a traction bracket. Furthermore the chain is supported by one end of the traction bracket at one side of the recovery and scattering trolley. The other end of the traction bracket is connected with the recovery and scattering trolley at a central position of the recovery and scattering trolley. The chain is connected with the recovery and scattering trolley through a cantilever state for traction. Through the structure of the invention, the recovery and scattering trolley can move with a stable state in single traction.