An RF amplifier to increase a gain using a transformer is provided. The amplifier includes: a first transistor configured to generate a current by amplifying and converting an input voltage; a second transistor configured to amplify the generated current; and a first transformer configured to feed an emitter current of the second transistor back to a gate. Accordingly, Gm of the transistor is boosted using the transformer, such that a high gain can be obtained with a low current. Therefore, a problem of a gain reduction caused by a parasitic capacitor at a high frequency can be solved.