An illumination device includes a light tube holder including two connectors for receiving either a light-emitting diode (LED) tube or a fluorescent tube. The connector includes a rotary member rotatably received in a through hole defined in a retainer, and three conductive elastic pieces positioned in the retainer around the through hole. One elastic piece is electrically connected to an LED tube drive circuit board, and the other two elastic piece are electrically connected to a fluorescent tube drive circuit board. The rotary member can be rotated to first and second positions, wherein at the first position, the LED tube can be activated, and at the second position the fluorescent tube can be activated. The LED tubes has two conductive pins at each end thereof. The LED tube can be mounted to the connectors regardless an orientation of the LED tube.