An optical recording/reproducing system comprising an optical pickup for recording and/or reproducing of data with respect to an optical recording medium. A reflection factor and a signal amplitude are obtained from the optical recording medium to be driven by the the recording/reproducing system. A reference level for detection of dirt deposition on the optical pickup is obtained on the basis of the reflection factor and signal amplitude information. The reference level for the dirt deposition is compared with a reproduction signal level obtained from the optical recording medium. A determination as to whether dirt is deposited or not is made on the basis of the comparison results.