Provided is a seam welding device capable of seam welding various shapes of objects to be welded. A seam welding device which performs seam welding by causing electricity to be conducted between a first electrode wheel and a second electrode wheel comprises a first motor which drives the first electrode wheel, a second motor which drives the second electrode wheel, and a first belt provided between the first electrode wheel and the first motor. If a direction joining the axes of the first electrode wheel and the second electrode wheel is defined as a vertical direction, the direction from the first electrode wheel toward the second electrode wheel is upward, and the direction from the second electrode wheel toward the first electrode wheel is downward, then the first motor is disposed further upward than a point of contact of the first electrode wheel and the second electrode wheel.