A Web browsing system where a Web browser function of displaying a Web page stored in a Web server on a user terminal (91-1, 91-2, 91-3) connected via the Internet to the Web server is divided into a browsing client unit and a browsing server unit, wherein the browsing client unit and the browsing server unit are connected to each other via a network, wherein the browsing client unit is installed in the user terminal (91-1, 91-2, 91-3) and notifies a content input to the user terminal (91-1, 91-2, 91-3) to the browsing server unit and display the Web page on the user terminal (91-1, 91-2, 91-3) by using information supplied from the browsing server unit, and wherein the browsing server unit supplies information necessary for displaying the Web page on the user terminal (91-1, 91-2, 91-3) to the browsing client unit according to the content input to the user terminal (91-1, 91-2, 91-3) notified from the browsing client unit, wherein the browsing server unit includes: an observation unit which transmits an observation request indicating a message of observing the communication environment, load and performance of the browsing client unit and acquires the communication environment, load and performance of the browsing client unit from the browsing client unit; and a a layout unit with a process decision unit which decides a process which is performed by the browsing server unit in order to display the Web page for each element of the Web page based on the communication environment, load and performance of the browsing client unit, wherein in a case where the processing time of the browsing client unit is short, the layout unit performs the process in the browsing server unit, and in a case where the load of the browsing client unit is small, the layout unit does not perform the process in the browsing server unit, wherein the decision of the process in the browsing server unit is performed by using one of the following indicators a) or b) or c): a) whether or not the performance of the browsing client unit is equal to or lower than a predetermined threshold value, b) whether or not the process load of the browsing client unit exceeds or reaches a predetermined threshold value in an average value or a peak value, c) whether or not the process load of the browsing server unit exceeds or reaches a predetermined threshold value in an average value or a peak value in a case where browsing server unit performs a portion of the process, wherein the browsing server unit performs the process decided by the process decision unit among information necessary for displaying the Web page on the user terminal (91-1, 91-2, 91-3) for each element of the Web page and supplies information necessary for displaying the Web page on the user terminal (91-1, 91-2, 91-3) to the browsing client unit, and wherein the browsing client unit returns an observation result according to the observation request from the browsing server unit and displays the Web page on the user terminal (91-1, 91-2, 91-3) by using the information supplied from the browsing server unit. an observation unit which transmits an observation request indicating a message of observing the communication environment, load and performance of the browsing client unit and acquires the communication environment, load and performance of the browsing client unit from the browsing client unit; and a a layout unit with a process decision unit which decides a process which is performed by the browsing server unit in order to display the Web page for each element of the Web page based on the communication environment, load and performance of the browsing client unit, wherein in a case where the processing time of the browsing client unit is short, the layout unit performs the process in the browsing server unit, and in a case where the load of the browsing client unit is small, the layout unit does not perform the process in the browsing server unit, wherein the decision of the process in the browsing server unit is performed by using one of the following indicators a) or b) or c): a) whether or not the performance of the browsing client unit is equal to or lower than a predetermined threshold value, b) whether or not the process load of the browsing client unit exceeds or reaches a predetermined threshold value in an average value or a peak value, c) whether or not the process load of the browsing server unit exceeds or reaches a predetermined threshold value in an average value or a peak value in a case where browsing server unit performs a portion of the process, a) whether or not the performance of the browsing client unit is equal to or lower than a predetermined threshold value, b) whether or not the process load of the browsing client unit exceeds or reaches a predetermined threshold value in an average value or a peak value, c) whether or not the process load of the browsing server unit exceeds or reaches a predetermined threshold value in an average value or a peak value in a case where browsing server unit performs a portion of the process, wherein the browsing server unit performs the process decided by the process decision unit among information necessary for displaying the Web page on the user terminal (91-1, 91-2, 91-3) for each element of the Web page and supplies information necessary for displaying the Web page on the user terminal (91-1, 91-2, 91-3) to the browsing client unit, and wherein the browsing client unit returns an observation result according to the observation request from the browsing server unit and displays the Web page on the user terminal (91-1, 91-2, 91-3) by using the information supplied from the browsing server unit.