This invention involves irradiating an optical disk with laser light, pulse-driven by a high-frequency signal from an HF oscillator, and converting the output of a photo-detector that receives laser light reflected from the optical disk into an electronic pulse readout signal using a current amplifier. The pulse readout signal is converted into a temporally continuous readout signal by a peak hold circuit. The invention solves the problems of SNR deterioration of the readout signal and the difficulty of removing the impact of high-frequency modulation accompanying the increase in the readout speed factor in optical disk devices.