A file sharing system connected to both a telephone network and a data communication network includes a telephone conversation state monitoring part for recording information for identifying speakers having a telephone conversation for each telephone conversation in a recording part as telephone conversation state data, a sharing space generating part for generating a file sharing space to a file sharing server for each telephone conversation, and recording information for identifying a file sharing space and information for identifying a speaker in a recording part in such a manner that they are associated with each other, and an access control part enabling access from a communication terminal by the speaker associated in the association data, among accesses from the communication terminals with respect to the file sharing Space. Because of this, the file sharing system allows a file to be shared with a party on the other side during a telephone conversation even without using a terminal with a particular function added thereto.