PROBLEM TO BE SOLVED: To provide a surface acoustic wave sensor capable of improving measurement accuracy and simply performing measurement and small in occupancy rate of a detection area.SOLUTION: The surface acoustic wave sensor includes a first surface acoustic element and a second surface acoustic element in order to perform differential detection when a variation of a target in an object to be measured is smaller than a variation by disturbance. The propagation distance of the second surface acoustic element is set corresponding to a ratio of the variation of the disturbance to the variation of the object to be measured to the propagation distance of the first surface acoustic element; the variation of the object to be measured in the second surface acoustic element is set to be smaller than the detection limit of the surface acoustic wave sensor; or the ratio of the variation of the disturbance to the variation of the object to be measured and the variation of the object to be measured in the second sur
