It is crucial that the manufacturing companies should consider reducing environmental impacts of the products in the early design phases. Life Cycle Assessment method is one of the most widely used and important tools for assessing the overall environmental impacts of products across the entire lifecycle. Based on the Life Cycle Assessment method, we provide a systematic guideline for eco-product design. The proposed guideline is primarily aimed at product developers or engineers, as a insight to the integration of environmental thinking into the early design phase, and therefore into products. This guideline has several steps: select the target product, describe the product structure, quantify the environmental impacts, identify meaningful underlying environmental impacts, and develop an environmental strategy. The usefulness of proposed guideline is also demonstrated through the application to an actual vacuum cleaner.