PROBLEM TO BE SOLVED: To provide a distance measuring device, a friction stir welding device, and a friction stir welding method capable of performing high-quality welding even on a work whose surface height fluctuates greatly. A distance measuring device moves in a first direction connecting a surface of a work and a shoulder surface in a state of being in contact with a contact surface of a welding tool for friction stir welding and a surface of the work. A measuring mechanism having a free tip part, a detector for detecting the position of the tip part in the first direction, and an output unit for outputting data of the position of the tip part in the first direction detected by the detector, and an output The controller includes a controller that calculates the position of the tip portion with respect to the contact portion from the position data output from the unit, and calculates the distance between the shoulder surface of the welding tool and the surface of the work. [Selection diagram] Figure 1
展开▼
