PURPOSE: To obtain the accuracy of an output signal higher than the attenuation amount accuracy of a digital attenuator.

CONSTITUTION: A signal from an input terminal (a) is attenuated with kn attenuation amount corresponding to the control data of a controller 15 at a digital attenuator 11, and its output signal is inputted to an analog attenuator 12, attenuated with the attenuation amount corresponding to a voltage generated by a D/A converter 13, and outputted from an output terminal (b). Since a ROM 14 stores the error correction contents of the digital attenuator 11 corresponding to the control data of the controller 15 and the analog attenuator 12 executes error correction, the high-accuracy output signal can be provided.