To solve such problems that, in conventional ring-bound desk calendars, three components of month sheets, a triangular mount, and a binder are integrally and mechanically bound, therefore, the desk calendars are advertisement goods that are annularly discarded and wastefully discarded separately or as a whole at the end of every year, and moreover, their binding costs in small lot production are high, and all defectively-bound calendars end up in the garbage, consequently, a novel leaf base device is required to benefit the three parties of users, sponsors, and manufacturers.

A novel trapezoidal container base and a novel paper-group hanging ring binder are manufactured. It is configured to provide a binder-type desk calendar of a product mounted with the binder on the top surface of the base to allow a user to renew the yearly calendar by the replacement paper. An article putting-in/taking-out port is provided in one face of a slope sidewall of a base body to form the desk calendar into a container of a pencil case. The container is assembled after injection molding a bottom lid component and an upper component. Further, advertisement with names of sponsors or the like is put on the sidewalls of the base product.