Provided are a migration apparatus and method for converting a database of a mainframe system into an appropriate database for an open system. The migration apparatus includes: a data extraction module connected with a database of the mainframe system and extracting data composed of Extended Binary Coded Decimal Interchange Code (EBCDIC) in binary format; a code conversion module converting the extracted EBCDIC data into American Standard Code for Information Interchange (ASCII) code, full-width characters being converted into half-width characters corresponding to ASCII code using a previously set full-width/half-width conversion table; and a data transfer module transferring the data converted into ASCII code to store it in a database previously built in the open system to correspond to the database of the mainframe system. The migration apparatus and method efficiently reuse a conventionally used database via the rehosting process of converting a mainframe system into an open system.