A multiple welding gun system includes a plurality of welding guns, simultaneously performing welding operations, mounted to a robot arm of a welding robot and a pitch changing device as a space adjusting device disposed between the plurality of welding guns. The pitch changing device is configured to change a gun pitch so as to adjust a space between the welding guns by rotating one of the welding guns relative to other one of the welding guns to thereby move the welding guns closer to or separate from each other.