Abstract: A multifunctional bag device according to this invention can be used not only as an ordinary bag, but also to provide a variety of functions by itself or with a sheet and hood contained in the bag. The multifunctional bag device of this invention includes a bag 1 consisting of right and left bag members 1a, 1b that is designed to contain appropriate things in it, a single sheet 2 which is contained in the bag 1 in a folded state, and a hood 3 formed so that it can be loaded on the upper portion of the sheet via fasteners. The bag 1 has handles 6 at the top, and edges of the right and left bag members are connected to each other at the bottom 4, and with a fastener 5 or other opening/closing device which allows the right and left bag members to be unfolded. The sheet 2 is equipped with a fastener 7 or other opening/closing device at peripheral edges to allow a bag 8 to be formed by folding the single sheet in half.