The present invention provides a deficiency detecting apparatus that can accurately detect dusts and deficiencies on an optical disk even when an emitting power of a laser light source changes. The deficiency detecting apparatus is provided with a deficiency detecting section for detecting deficiencies or the like on an optical disk by reflected light, and a power adjusting section for adjusting an emitting power of a laser light source to be an optimum value. The deficiency detecting section can accurately detect the deficiencies on the optical disk even when the laser power changes by comparing a threshold value, which is determined in accordance with the adjustment result of the power adjusting section, with a value in accordance with the reflected light.