To stably store books stably in an optional position without requiring much time and trouble even when a gap is provided in a book shelf.

This stored material support device is provided in a storing space S. The device includes a plurality of support pieces 3 juxtaposed in the vertical direction to be pushed in and returned. The support pieces 3 of a number corresponding to the width of the stored material B are pushed in the stored material B inserted in the storing space S, and the inserted stored material B is supported from both sides by the respective support pieces 3 remaining on both sides of the pushed support pieces 3.