An illumination device includes a light tube holder including two connectors for receiving either a light-emitting diode (LED) tube or a fluorescent tube. One of the connectors includes a rotary member rotatably received in a through hole defined in a retainer, and four conductive elastic pieces positioned in the retainer around the through hole. Two of the conductive pieces are electrically connected to an LED tube drive circuit board and the other two are 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.