Abstract: A flexible door comprising a tough, nonelastic flexible sheet and a plurality of straight, plate-like unit blocks, each having a rectangular section and each being adhered to the sheet, the blocks being arranged side-by-side in contact with each other. The door is fixed to a post at one end and has a handle at the other end. When one side of the door formed by the unit blocks is pressed on, the side surfaces of adjacent unit blocks intimately contact each other, permitting the nonelastic sheet to keep the door planar in a closed position. When the handle on the other side, namely, on the sheet side, is pulled, the door flexes to an open position within a narrow space. The door can be installed in the same manner as a swing door without the necessity of providing a special guide and fixture on the lintel, floor, sill, etc.