To provide an optical disk drive which can easily discriminate whether a recording surface of an optical disk and an objective lens of an optical pickup are contaminated by attachment of a foreign substance such as dust by detecting decrease of the amount of return light from an optical disk.

The optical disk drive periodically records the amount of return light from a standard medium as the amount of standard return light on a nonvolatile memory for recording by housing a standard medium protected with a cover for preventing dust adhesion, and compares the amount of return light from the optical disk and the amount of the return light from the standard medium when an error occurs. When the amount of the return light from the optical disk is smaller than the amount of return light from a standard medium by more than a specified value, and the amount of the return light from the standard medium and the amount of the standard return light are almost equal, it is determined that the used optical medium is contaminated. When the amount of the return light from the standard medium is smaller than the amount of the standard return light by more than the definition value, it is determined that the optical pickup is contaminated.