PURPOSE: To perform the operation with a mouse without modifying application by converting data from the mouse to a series of key data based on mouse data conversion information to input this data to an application program as key data.

CONSTITUTION: When data is inputted from a mouse 4 to a mouse data input means 1, a data converting means 2 receives input data of the mouse 4 from the input means 1 and reads out mouse data conversion information (contents are different by application programs) for conversion of this input data from the mouse to key data from a hard disk device 5 and converts input data from the mouse to a series of key data based on read-out mouse data conversion information. Converted key data is transferred to a key buffer 6 of the application program by a data converting means 3. The application program recognizes the key input to obtain key data through the key buffer 6 and performs the operation corresponding to this data.