A desk leaf base has a base formed of a trapezoidal tubular body in a trapezoidal shape in a side view, closed from a bottom surface to a certain height in both sides, and opened in an upper portion therefrom. An inclined front wall of the tubular body is removed from one side to the other side, in a range from the height to a higher height lower than a top surface. A binder mounted along an elongated top surface of the base has an elongated body and rings. The elongated body is mounted along the top surface of the base with an approximately same width as the top surface. The rings are mounted on the body and capable of opening and closing. Each ring includes linear portions that protrude from the body inclining upward on front and back sides when closing.