The present invention discloses a flexible LED device and a flexible LED panel. Differing an approach for substrate lift-off and bonding is conventionally adopted to exchange a sapphire substrate of an LED die for a copper substrate having excellent thermal conductivity, this novel flexible LED device is constituted by a thin-metal-made substrate, a substrate protection layer, a lattice matching layer, a light-emitting structure, a first electrode, and a second electrode. It is worth explaining that, thanks to that the thin-metal-made substrate with a thickness in a range from 25 μm to 150 μm exhibits outstanding mechanical characteristics including flexibility, thermal conductivity and thermal resistance, engineers can adopt thin film deposition technologies such as PECVD and MOCVD as well as utilize roll-to-roll manufacturing systems to mass produce this flexible LED device. Besides, heat produced during the illumination of the flexible LED device can be effectively dissipated by the thin-metal-made substrate.