Disclosed is a light emitting diode (LED) device that comprises a crystal structure of a sapphire substrate-free gallium nitride (GaN) LED, wherein the crystal structure is mounted on a first surface of a sub-mount substrate in the form of a unit chip, and the first surface of the sub-mount substrate has a surface area greater than the surface area of a region in which the unit chip is bonded. Preforms for manufacturing the LED device and a method for manufacturing the LED device are also disclosed. The sapphire substrate, on which the crystal structure of the light emitting diode has grown, is processed into a unit chip before being removed. Thus, any crack in the crystal structure of the light emitting diode that may occur during the removal of the sapphire substrate can be prevented. Therefore, a thin light emitting diode device can be manufactured in a mass production system.