A test device for testing a digital to analog converter includes a gamma reference unit for generating a plurality of analog signals different from each other; a temporary storing unit for generating a plurality of digital signals different from each other; a decoder for selecting one of the plurality of analog signals or one of the plurality of digital signals in response to a digital code signal; and a switching unit for controlling a connection between the decoder and the gamma reference unit and between the decoder and the temporary storing unit according to an operation mode.