An information recording/reproducing apparatus includes a detector circuit for detecting a state of reflection light from the recording medium, a control circuit for calculating a radiation power used for writing the information in the recording medium, in accordance with the reflection light state, a pulse generator circuit for generating record pulse information in accordance with the radiation power, and an optical driver circuit for converting the record pulse information into optical information in accordance with the radiation power and driving the optical head to record the light information into the recording medium. Accordingly, the apparatus records information by applying light from an optical head to a record area of a recording medium and changing a state of the record area and reads the information recorded in the record area.