In an optical disk apparatus, recording information by irradiating a laser light from a laser diode LD upon a recording surface thereof, while rotationally driving an optical disk by means of a spindle motor 207, being provided with a front monitor diode FMD for monitoring the laser light from the LD therein, a controller portion 205 detects deterioration of the laser diode, including the kink phenomenon, in particular, of loosing the linearity in the driving characteristic thereof caused due to driving under the condition of high temperature, by comparing a laser light output detected by the FMD to that, which is detected previously, within recording operation of the apparatus, and it also makes controls to lower the rotation velocity of the optical disk. This is suitable, in particular, to the optical disk apparatus of a super or ultra-thin type.