To provide a data providing system in which the server side surely detects the fact that the downloading of a file has been completed on the user's side, then a key file is transmitted to unlock the copy protect and conducts a charging process.

The system is provided with terminal devices 20a and 20b which are PCs that have a client function and receive purchasing information of data files and user's personal information, portable terminals 20c which are portable telephones or the like that have a client function and receive the purchasing information of data files and user's personal information, a data providing device 10 which has a server function and provides the data files based on the purchasing information and the personal information and a computer network 30 such as Internet which connects the terminals 20a to 20c and the device 10.