An attenuator includes a first diode, a first control voltage terminal, a second diode, a first resistance, a second resistance, a third diode, a fourth diode, a fifth capacitance, a second control voltage terminal, a third control voltage terminal, a fourth control voltage terminal, and a linearizer provided between an input terminal and the anode of the first diode. The linearizer linearizes a signal input to the input terminal only when low level voltages are applied to the first and fourth control voltage terminals at the same time that high level voltages are applied to the second and third control voltage terminals.