A communication terminal apparatus, server, and radio communication system are provided that implement communication in a specific area subject to radio signal restrictions. The server 200 is equipped with a control section 201, a terminal control section 202, a database RAM section 203, a signal conversion control section 204, an ad hoc TX 205, an ad hoc RX 206, a radio TX 207, and a radio RX 208; mobile radio terminals 110 and 120 are equipped with a terminal function control section 111, a peripheral section 112, an ad hoc TX 113, an ad hoc RX 114, a radio TX 115, and a radio RX 116; and server 200 constructs a radio ad hoc network by means of terminal-server connection, and also transmits a control signal including inhibition of connection to a base station 300, and establishes ad hoc network connection on receiving a control signal from server 200.