Provided are an optical pickup device, which is capable of detecting and correcting spherical aberration while suppressing an increase in the number of construction elements and without increasing outer dimensions of a pickup device main body, and a recording and/or reproducing device having the optical pickup device built therein. A lens is designed such that when the thickness of a disk protective layer is greater than an optimum value, returning light (reflection light) from a disk is condensed on a sensor. The sensor is arranged at a condensing point and has a shape with which around 50% of the returning light is received when the thickness of the protective layer assumes the optimum value. With this construction, the quantity of light received by the sensor is increased when the thickness of the protective layer is greater than the optimum value, and is conversely reduced when the thickness of the protective layer is smaller than the optimum value. As a result, it becomes possible to detect the direction and degree of a thickness error with reference to the magnitude of an output from the sensor and to correct spherical aberration based on a result of the detection.