The invention relates to a clock generation circuit and a signal reproduction circuit including the clock generation circuit, and, more particularly, the invention provides a data judgment/phase comparison circuit capable of performing both of data judgment and phase comparison by a single-phase clock, and provides a CDR (Clock Data Recovery) circuit including the data judgment/phase comparison circuit. The same data and clock are inputted to two data judging units C_GOOD and C_BAD each having a different data determination period (setup/hold time) required for correctly judging a data, and an output of the data judging unit C_GOOD having a shorter required data determination period is taken as a data output of the data judgment/phase comparison circuit. When the outputs of both of the data judging units are different from each other, a signal Early indicating that a clock phase is too early or a signal Late indicating that the clock phase is too late is outputted. Depending on a relation among data outputs of total three symbols obtained by combining a symbol and symbols previous and subsequent thereto, it is selected that either the Early or the Late is to be outputted by a decision logic EL_LOGIC.