In a method of transforming a recording power level into multi-levels by using an extra recording power level, the optimum value of each recording power level is obtained, thereby achieving recording with good accuracy. By including a first test writing step (S1–S3) of performing test writing of predetermined first test data while varying the recording power in stages, and calculating an optimum recording power from the reproduction signal, and a second test writing step (S4–S6) of setting the recording power to the calculated optimum recording power and performing test writing of predetermined second test data while varying in stages the extra recording power applied in a part of a time period in which the optimum recording power is applied, and calculating an optimum extra recording power from the reproduction signal, the recording power and the extra recording power are separately calculated by test writing, and with which information is recorded. Hence, it is possible to form the shape of a recording mark and the mark position with good accuracy. Thus, recording can be performed with good accuracy.