A clock adjustment circuit and a digital to analog converting device are provided. The clock adjustment circuit includes a selection circuit and a frequency decreasing circuit. The selection circuit is configured to generate a first selection signal in response to a frequency of an output clock signal. The frequency decreasing circuit is coupled to the selection circuit, and configured to generate the output clock signal by reducing a frequency of an input clock signal by a first ratio in response to a first level of the first selection signal, and configured to generate the output clock signal by reducing the frequency of the input clock signal by a second ratio in response to a second level of the first selection signal, wherein the first ratio is different from the second ratio. Accordingly, complexity of a circuit is reduced.