Abstract: A folding suitcase includes a back case component, a front lid component, a peripheral side wall component, and a fold-resisting component. An accommodating space formed by the peripheral side wall component, the back case component and the front lid component is for being covered selectively. The peripheral side wall component has multiple first sidewall parts, multiple second sidewall parts and multiple bending parts connected to the multiple sidewall parts and the multiple second sidewall parts. The multiple bending parts are bendable to allow the multiple first sidewall parts and the multiple second sidewall parts to be folded oppositely or erected on the back case component. The fold-resisting component is elastic and includes a combined part and an extension part. The combined part is disposed at the multiple first sidewall parts. The extension part is detachably disposed at the multiple bending parts for selectively supporting the peripheral side wall component.