A communication unit includes the following elements. A first transmit circuit outputs a first signal or a second signal from a first input signal. A first amplifier amplifies the first signal and outputs a first amplified signal. A first signal generating circuit generates a third signal having a frequency higher than a frequency of the second signal, based on the second signal and a first reference signal. A first filter circuit receives the third signal and allows one of a frequency component representing a sum of the frequency of the second signal and a frequency of the first reference signal and a frequency component representing a difference therebetween to pass through the first filter circuit and attenuates the other one of the frequency components. A second amplifier amplifies the third signal output from the first filter circuit and outputs a second amplified signal.