A data join system of the present invention includes a table determination unit 11 selecting a record b as a join target if a value of a key item included in a record a acquired by a data write unit from a table A falls within a first predetermined range set based on a value of a key item included in the record b stored in a table B, a data join unit joining the selected record b with the record a to generate a record c, and a data write unit storing the record c into a table C. Thus, the success rate of data join can be improved while the accuracy of join of the record b and the record a to be joined is improved.