PURPOSE: To assembly a knapsack to make it into a simple studying desk by building two legs in a cover to cover a main body, stretching the cover from the main body horizontally, turning the legs in making a rotary shaft into a center, and making the main body, cover and legs into a inverse U-shape when the legs are made right-angle to the cover.

CONSTITUTION: In order to cause a knapsack 1 main body to easily stand vertically, the bottom part is made flat. A cover 2 is the cover of the main body 1, two legs 3 and 4 are built in along the surface, the legs 3 and 4 are coupled to rotary shafts 5 and 6 at two points provided in the peripheral part of the cover 2, and they are rotated in making the shafts into the centers. At the time of using it for a seating desk, the cover 2 is stretched from the main body 1 to a rear side horizontally. At such a time, the two legs 3 and 4 housed in the cover 2 are rotated in making the rotary shafts 5 and 6 into supporting points, and they are made right-angled to the cover 2. In such a condition, the knapsack is made into an inverse U-shape. Thus, since the knapsack can be easily made into the studying desk, study can be executed by moving to a veranda in day time and in a living roon at night.