Abstract: [Problem] To provide a foldable frame structure, unfoldable into a 2N-sided polygonal shape (N being an integer equal to or larger than 2), achieving a securely and rigidly supported unfolded state and a compact folded state. [Solving means] 2N upper rods (210), with an equal length, are coupled to each other to define a planer 2N-sided polygonal shape. First coupling means (220) coupling two adjacent upper rod (210) at a corresponding one of apices of the 2N-sided polygonal shape, and holding the two upper rod (210) in such a manner that the upper rod (210) are rotatable about an orthogonal axis orthogonal to axes of both of the two rods and rotation means (240) that enable each of the upper rods (210) to rotate about the axis (AX1) are provided. Folding to be a columnar shape as a whole can be achieved with the upper rods (210) pivoted about the orthogonal axis (AX2) to minimize an angle between two adjacent upper rods (210) while the upper rods (210) are rotated about the axis (AX1).