According to the present invention, when a style relating to a dimension of all elements included in a subtree of a structured document is set in a relative unit, all these elements can be displayed in the same style. The user terminal 100 allocates a drawing area to each key when drawing each key configuring a key string of a tree structure, determines a root of a subtree to which a specific key belongs when a style whose format relating to dimension is expressed in the relative unit is set to the key, and converts the style expressed in the relative unit into an absolute unit with the drawing area allocated to the root of the subtree as reference and draws the key according to style expressed in the absolute unit.