A data exchange system comprising: a base database configured to store attribute data included in an attribute item indicating an attribute in association with a base code of the attribute data; an item mapping unit configured to, when input-side external data is stored in an input-side external database and includes input-side external attribute data corresponding to an input-side external attribute item indicating an attribute of the input-side external data, associate the attribute item corresponding to the input-side external attribute item with the input-side external attribute item, and to, when output-side external data is stored in an output-side external database and includes output-side external attribute data corresponding to an output-side external attribute item indicating an attribute of the output-side external data, associate the attribute item corresponding to the output-side external attribute item with the output-side external attribute item; a code mapping unit configured to associate the input-side external attribute data with the base code included in the attribute item associated with the input-side external attribute item to which the input-side external attribute data belongs by the item mapping unit, and to associate the output-side external attribute data with the base code included in the attribute item associated with the output-side external attribute item to which the output-side external attribute data belongs by the item mapping unit; characterized by further comprising a standard data conversion unit configured to convert the input-side external data into standard data (120, 122) configured by the attribute data associated with the base code associated with the input-side external attribute data; and a conversion unit configured to refer to the base code associated with the output-side external attribute data, and to convert the input-side external data into output data for the output-side external database, using the attribute data corresponding to the base code and included in the standard data (120, 122). a base database configured to store attribute data included in an attribute item indicating an attribute in association with a base code of the attribute data; an item mapping unit configured to, when input-side external data is stored in an input-side external database and includes input-side external attribute data corresponding to an input-side external attribute item indicating an attribute of the input-side external data, associate the attribute item corresponding to the input-side external attribute item with the input-side external attribute item, and to, when output-side external data is stored in an output-side external database and includes output-side external attribute data corresponding to an output-side external attribute item indicating an attribute of the output-side external data, associate the attribute item corresponding to the output-side external attribute item with the output-side external attribute item; a code mapping unit configured to associate the input-side external attribute data with the base code included in the attribute item associated with the input-side external attribute item to which the input-side external attribute data belongs by the item mapping unit, and to associate the output-side external attribute data with the base code included in the attribute item associated with the output-side external attribute item to which the output-side external attribute data belongs by the item mapping unit; characterized by further comprising a standard data conversion unit configured to convert the input-side external data into standard data (120, 122) configured by the attribute data associated with the base code associated with the input-side external attribute data; and a conversion unit configured to refer to the base code associated with the output-side external attribute data, and to convert the input-side external data into output data for the output-side external database, using the attribute data corresponding to the base code and included in the standard data (120, 122).