To execute efficient data access control by bypassing a server function part driven by a file system for data retrieval, access control, etc., and directly transferring data from an IO function part to a client.

In the data access control system constituted of the client 1 requiring data access, a server function part 2 connected to the client 1 and retrieving the storage position of data in accordance with a request from the client 1 and an IO function part 3 connected to the server function part 2 and storing the request data from the client 1, the IO function part 3 is directly connected to the client 1 through a line 4, the server function part 2 transfers a key necessary for a connection permission procedure prepared on the basis of the data request from the client 1 to the client 1 and the client 1 directly transfers data to the IO function part 3 through the line 4 by using the transferred key.