An optical disk apparatus, which greatly decreases probability of impossibility of correcting an error in reading, is provided, where the error results from deviation of a writing-resuming position in resumption of writing. When an amount of data in a buffer becomes not more than a given amount of data, a buffer-underrun-detecting-circuit judges that the data are in a buffer-underrun-condition. According to the judgement, a writing-interrupting-and-resuming-circuit detects an end position of the last pit for writing, and the position is stored in a time-information-memory, and the optical disk apparatus becomes in a pause condition of writing. When the buffer-underrun-condition is avoided, the optical disk apparatus releases the pause condition of writing, and reads the position of interruption of writing from the time-information-memory, and then synchronizes data written on an optical disk and the data for writing. After that, writing is resumed with a given interval formed between the data written and the data for writing.