Simple, rapid and low-cost assembly methods of a LED lamp are provided. A standard lamp base having two electrodes and a cavity is soldered with a resistor to the first one of the electrodes, and then filled with a thermally conductive electric insulator in the cavity. A circuit board is attached onto the thermally conductive electric insulator and then soldered to the second electrode and the resistor. An LED device is soldered onto the circuit board such that the LED device and the resistor are serially connected between the electrodes. Preferably, the circuit board has a through hole through which a thermally conductive member is inserted into the thermally conductive electric insulator with its lower end, and the LED device is placed onto the upper end of the thermally conductive member.