Abstract: An optical disk recorder has a clock signal generator which switches between a reproducing clock signal and a recording clock signal. The optical disk recorder records data from the end point of the recorded data after interruption of recording due to buffer under-run phenomenon. In this recording, the optical disk recorder reads out a read clock signal from the recorded data, detects the end point of the recorded data and then starts for recording from the end point based on a recording clock signal, Switching between the reproducing clock signal to the recording clock signal allows a linear change in the output frequency to thereby improve the continuity of the recorded data in the vicinity of the end point.