Treatment of dilute-organic wastewater discharged from semiconductor manufacturing facilities using photocatalytic degradation mediated by illuminated TiO2 was experimentally investigated. An organic solvent, ethyl lactate was evaluated due to its common application in various wafer fabrication process. The optimal operating conditions (e.g., TiO2 dosage and pH) for the photocatalytic oxidation of ethyl lactate were determined. Photocatalytic degradation under these optimal conditions was found to be able to simultaneously mineralize ethyl lactate and remove copper(II) in the synthetic wastewater. Under aerobic conditions, oxygen inhibited copper reduction and copper(II) ions were removed through precipitation. In contrast, for reactions under anaerobic conditions, the removal rate of copper(II) ions and the rate of reduction of the TOC content are lower than that in the aerobic conditions. Hence the application of photocatalysis in simultaneously reducing copper(II) and the TOC content of wastewater discharged from semiconductor industry is worth developing further to improve the efficiency of the reaction.