A ratio of an erase current and a peak current when starting recording is defined as K=iER/iPK (S1), and iER11 is set equal to K×iPK1, and an ideal value iER11 of an erase current that should be increased according to a temperature change is determined (S2). A value obtained by subtracting a current iBT at a bottom level emission intensity when starting recording from a current at an erase level emission intensity after the temperature rises is defined as iER1. By measuring this iER1, an ideal value iER11 of the erase current is subtracted from iER1, and the resultant current is defined as iBT11 (S3). This iBT11 is set as an adjustment value of the bottom current, and a value obtained by adding this adjustment value to a bottom current when starting recording is set as a bottom current after change.