To provide a movable partition device which can be used not only as a partition for an indoor space but also as a storage, which enables the stable attachment of a shelf board when used as the storage, and which has a simple structure and a good appearance.

This movable partition device is equipped with a plurality of partition walls 6 and 6 with a plurality of lateral grooves 32 and 32. When the partition walls 6 and 6 are put into the partitioning state of partitioning the indoor space 1, the lateral grooves 32 and 32 of the adjacent partition walls 6 and 6 continue in a lateral direction. When the partition walls 6 and 6 are put into the state of being used as the storage, both side ends of the shelf board 10 are inserted into the lateral grooves 32 and 32 of the opposed partition walls 6 and 6, so that the shelf board 10 can be attached.