A structured document signature device includes an adaptation policy associator configured to associate each element forming a structured document with an adaptation policy indicating an action which can be adapted to a child element of the element or a value of the element; a hash tree constructor configured to insert a hash value of the child element of the element or a hash value of the value of the element into the structured document as an attribute value of the element, and to construct a hash tree including the hash value; a digital signature adder configured to add a digital signature to a root of the hash tree and the adaptation policy; and an output configured to output the structured document and the digital signature.