The present invention relates to a method for determining the power of a laser beam, a method for determining a critical parameter used for determining the power of a laser beam, an optical recording medium and a data recording apparatus and, particularly, to a method for determining the power of a laser beam which can determine the recording power of the laser beam so that jitter of a reproduced signal obtained by reproducing data recorded in a data rewritable type optical recording medium can be controlled within a tolerance even when cross erasing of data occurs and that the reproduced signal having the highest level can be obtained, a method for determining a critical parameter used for determining the power of a laser beam which can determine the recording power of the laser beam to be projected onto a data rewritable type optical recording medium so that jitter of a reproduced signal obtained by reproducing data recorded in the data rewritable type optical recording medium can be controlled within a tolerance even when cross erasing of data occurs and that the reproduced signal having the highest level can be obtained, a data rewritable type optical recording medium in which a critical parameter used for determining the power of a laser beam which can determine the recording power of the laser beam so that jitter of a reproduced signal obtained by reproducing data recorded therein can be controlled within a tolerance even when cross erasing of data occurs and that the reproduced signal having the highest level can be obtained, a data recording apparatus storing a critical parameter used for determining the power of a laser beam which can determine the recording power of the laser beam to be projected onto a data rewritable type optical recording medium so that jitter of a reproduced signal obtained by reproducing data recorded in the data rewritable type optical recording medium can be controlled within a tolerance even when cross erasing of data occurs and that the reproduced signal having the highest level can be obtained, and a data recording apparatus storing an optimum recording power of a laser beam to be projected onto a data rewritable optical recording medium so that jitter of a reproduced signal obtained by reproducing data recorded in the data rewritable type optical recording medium can be controlled within a tolerance even when cross erasing of data occurs and that the reproduced signal having the highest level can be obtained.