Resistance welding device and resistance welding method

The invention discloses a resistance welding device. The resistance welding device comprises a pair of electrodes, a retainer, a spraying opening and an elastic component, the pair of electrodes sandwiches the rivet and the plurality of metal members. The pair of electrodes is composed of a first electrode and a second electrode. The holder is configured such that a portion including a distal end facing an outermost metal member located on the first electrode side among the plurality of metal members is movable in a pressing direction and a direction opposite to the pressing direction with respect to the first electrode, and the rivet is held at the portion including the distal end. The ejection port ejects air in the pressurizing direction from the inside of the holder toward the outermost metal member. The elastic member biases the holder in the pressing direction by a biasing force, and the biasing force is smaller than a reaction force generated in the opposite direction on the holder due to the ejection