In an operation support system 1 according to the present invention, a first operation room 1A, a second operation room 1B, a third operation room 1C, . . . , a conference room 1D, and the like are connected by an IP network via an operation room communication line 8, are connected to the Internet by a WEB server 7 via an in-house communication line 6, and are externally connected via a communication line 9. A first controller 3 in the first operation room 1A has a table for registering an IP address for permitting the connection to a connecting request destination which requests the connection. A determining device 2 in the first operation room 1A determines whether the connection to the connection request destination is permitted or refused depending on the presence or absence of the IP address registered in the table when the connection request destination requests the connection.