A flexible electronic device is provided in this disclosure. The flexible electronic device includes a base layer, an electronic unit, and a cover layer. The electronic unit is disposed on the base layer, and the cover layer is disposed on the electronic unit. The base layer has a thickness T1 and a Young's modulus E1, and the cover layer has a thickness T2 and a Young's modulus E2, wherein the thickness T1, the thickness T2, the Young's modulus E1, and the Young's modulus E2 comply with following expression: E2/E1≤156.21×(T2/T1)−4.28.