To provide a panel device capable of developing from a nubby folded state to a large planar state.

The panel device comprises a plurality of panel bodies 11 and each panel body 11 has a plurality of panel pieces 12. Connection means connect the panel bodies 11 to each other and also connect the panel pieces 12 to each other. Each panel body 11 is capable of primary-developing from a housed state that the panel pieces 12 are overlapping each other (Fig. 1B(1), not shown here) to an intermediate state that the panel pieces are aligned in a planar state (Fig. 1C(3), not shown here) by extending to the overlapping direction Y of the panel pieces in the housed state. Each panel body 11 is capable of secondary-developing from the intermediate state to a developed state that the panel bodies are aligned in a planar state (Fig. 1D(5), not shown here) by extending to the overlapping direction Z of the panel bodies 11 in the intermediate state.