A Web-screen sharing system including a first and a second terminals, and a mediation server. The system includes: the terminals exchanging addresses through the mediation server; connecting the terminals using the addresses; when the first terminal is connected to any Web server, detecting whether a content in the Web server is security-protected; if protected, performing predetermined authentication processing with the Web server; when the authentication is successful, the Web server transmitting a content following the authentication processing to the first terminal; the first terminal displaying the content as a Web screen, and capturing the Web screen; transmitting an image file of the Web screen to the second terminal to display the screen on the second terminal, if not protected, the first terminal receiving the content from the Web server, and transmitting a URL at that time to the second terminal to display the Web screen.