A write-once high density optical recording medium capable of a high speed recording that effectively forms space between recording marks. A recording layer 18 of a high speed write-once optical recording medium 10 is formed by laminating a first sub recording layer 18A and a second sub recording layer 18B each containing a metal as its main component. When the recording layer (laminated recording layer) 18 is irradiated with a laser beam, the main component metals contained in the first and second sub recording layers 18A, 18B diffuse and are mixed together by means of the irradiation, thereby forming recording marks whose reflectance have been irreversibly changed due to such mixing. At this time, after an irradiation using a laser beam for forming recording marks, a power level P1 lower than a read power is maintained for a predetermined time Ti.