An LED bulb includes a bulb body and an adapter detachably connecting with the bulb body. The bulb body has two pins function as a negative electrode and a positive electrode. The two pins are for inserting into and electrically connecting with a bi-pin socket connector for light bulb, such as MR16 socket connector. The adapter includes a junction seat, a first connector, a second connector, and a bulb cap. Metallic threads are formed on the bulb cap. The first connector is received in the junction seat and electrically contacts the threads. The second connector extends through the junction seat and the bulb cap to make a bottom end thereof being exposed. The adapter is able to engage and electrically connect with an Edison screw socket connector, for example, E-10 socket connector.