A low noise amplifier is provided. The low noise amplifier includes: a low noise amplifying unit amplifying an input signal; a harmonic and noise generating unit disposed in an input terminal of the low noise amplifying unit, for generating a compensating signal for compensating for an intermodulation distortion signal and a thermal noise signal of the input signal to the low noise amplifying unit; and a load unit outputting the amplified input signal generated by the low noise amplifying unit.