A color-temperature adjustable light-emitting diode (LED) lighting device and a method for adjusting the color temperature of an LED lighting device are provided. The color-temperature adjustable LED lighting device includes: a power supply module, a micro-control unit (MCU), an adjustable LED driving power supply having a positive output terminal and a negative output terminal, a cool white LED array, a warm white LED array, a first switch circuit, a second switch circuit, a first current detection circuit, and a second current detection circuit. The power supply module is connected to an input terminal of the MCU and an input terminal of the adjustable LED driving power supply.