1. A user interface (UI) creation support system that supports creating a UI screen for receiving an input of each of a plurality of items, the UI creation support system comprising: a processing unit including a CPU; a UI configuration determining unit that arranges graphical user interface (GUI) components for receiving an input of each of the plurality of items and item-relevant information pieces which are information pieces relevant to the plurality of items which are displayed in correlation with the GUI components on the UI screen, that adjusts an amount of the item- relevant information pieces to be arranged on the UI screen depending on an assumed user using the UI screen, and that determines a configuration of the UI screen for the assumed user, wherein the item-relevant information pieces have a hierarchical structure including a lower layer having item identification information pieces for identifying the plurality of items and at least one upper layer having a plurality of groups into which the item identification information pieces are classified, and wherein the UI configuration determining unit arranges the item identification information pieces on the UI screen and adjusts an amount of information of the upper layer to be arranged on the UI screen, wherein the UI screen is a UI screen for inputting information on a predetermined service, and wherein the UI configuration determining unit increases an amount of the item-relevant information pieces to be arranged on the UI screen when a level of proficiency of the assumed user at the predetermined service is low, and decreases the amount of the item-relevant information pieces to be arranged on the UI screen when the level of proficiency of the assumed user at the predetermined service is high, wherein the amount of the item-relevant information pieces includes information about the upper layer of the hierarchical structure having the plurality of groups.