An exclusive control system comprising: a plurality of terminals (110, 110A, 110B) and a server storing predetermined data which can be accessed by each of the plurality of terminals (110, 110A, 110B), the exclusive control system being configured to restrict simultaneous access from the plurality of terminals (110, 110A, 110B) to the predetermined data, wherein each of the plurality of terminals (110, 110A, 110B) includes: a process executor which is configured to set on the server an access right to define an exclusion period during which one terminal can access the predetermined data while access thereto of another terminal is restricted, and which is configured to execute an updating process for updating the exclusion period before the exclusion period elapses; and a determiner which is configured to determine access to the predetermined data as being restricted in the case of an access within the exclusion period b defined by another terminal and which is configured to determine access to the predetermined data as being not restricted in the case of an access outside the exclusion period, wherein the process executor, when accessing the predetermined data, is configured to create on the server an authentication file having a valid period which is the exclusion period and to update the authentication file before the valid period elapses, and wherein the determiner is configured to determine access to the predetermined data as being restricted if the authentication file created on the server by another terminal is within the valid period, and to determine access to the predetermined data as being not restricted if the authentication file created by another terminal is not present on the server or if the valid period of the authentication file created on the server by another terminal has elapsed. a plurality of terminals (110, 110A, 110B) and a server storing predetermined data which can be accessed by each of the plurality of terminals (110, 110A, 110B), the exclusive control system being configured to restrict simultaneous access from the plurality of terminals (110, 110A, 110B) to the predetermined data, wherein each of the plurality of terminals (110, 110A, 110B) includes: a process executor which is configured to set on the server an access right to define an exclusion period during which one terminal can access the predetermined data while access thereto of another terminal is restricted, and which is configured to execute an updating process for updating the exclusion period before the exclusion period elapses; and a determiner which is configured to determine access to the predetermined data as being restricted in the case of an access within the exclusion period b defined by another terminal and which is configured to determine access to the predetermined data as being not restricted in the case of an access outside the exclusion period, wherein the process executor, when accessing the predetermined data, is configured to create on the server an authentication file having a valid period which is the exclusion period and to update the authentication file before the valid period elapses, and wherein the determiner is configured to determine access to the predetermined data as being restricted if the authentication file created on the server by another terminal is within the valid period, and to determine access to the predetermined data as being not restricted if the authentication file created by another terminal is not present on the server or if the valid period of the authentication file created on the server by another terminal has elapsed. a process executor which is configured to set on the server an access right to define an exclusion period during which one terminal can access the predetermined data while access thereto of another terminal is restricted, and which is configured to execute an updating process for updating the exclusion period before the exclusion period elapses; and a determiner which is configured to determine access to the predetermined data as being restricted in the case of an access within the exclusion period b defined by another terminal and which is configured to determine access to the predetermined data as being not restricted in the case of an access outside the exclusion period, wherein the process executor, when accessing the predetermined data, is configured to create on the server an authentication file having a valid period which is the exclusion period and to update the authentication file before the valid period elapses, and wherein the determiner is configured to determine access to the predetermined data as being restricted if the authentication file created on the server by another terminal is within the valid period, and to determine access to the predetermined data as being not restricted if the authentication file created by another terminal is not present on the server or if the valid period of the authentication file created on the server by another terminal has elapsed.