A wall socket aroma diffuser using an aroma capsule is provided, including a wall socket aroma diffuser having a transparent receiving unit and an aroma capsule received in the wall socket aroma diffuser. The aroma capsule is heated to diffuse scent, and is disposable after the aroma thereof is diffused into an ambient environment completely. It is thus easy, safe for a user to replace the used aroma capsule with a new one because the aroma capsule will not be broken and the aroma thereof will not flow to a region outside of the aroma capsule. The user does not need to wash the aroma diffuser. The wall socket aroma diffuser further includes a light emitting diode that emits and projects light onto the transparent receiving unit. The light is guided and diffused by the receiving unit to generate color that pleases people's eyes.