Abstract: An interactive speech interface unit includes speech recognizer for recognizing input speech of user utterance and converting the recognized input speech into a character string; an input statement analyzer means for analyzing the character string and converting the analyzed character string into semantic representation; an interactive controller for controlling flow of an interactive status and accessing an application; an output statement generator for generating an intermediate language to be output to the user; a speech generator for converting the intermediate language into speech and outputting the speech; and an application interface for accessing the application using the semantic representation output from the interactive controller, wherein the interactive controller puts series of interactive sequences having calling relations together in a plurality of interactive tasks in association with relations and includes an interactive task hierarchical data base for storing the interactive tasks in a hier