This study analyzed the trends of patents for unmanned technology used in agriculture. The target countries for this survey of patent data were Korea, the USA and Japan as well as the countries in Europe. The indices used in this study to analyze the patents were the CPP (Cites Per Patent), PII (Patent Impact Index), and PFS (Patent Family Size). The total effective patents for unmanned technology used in agriculture were 1,080 cases. The number of patents in the USA, Japan, Europe, and Korea were 541, 326, 128 and 85 cases, respectively. Among the total effective patents, the evaluation scores for selected important patents were calculated by applying commonly used weights to each index, and the top 10 patents were selected as important patents. The results showed that all the top ten patents are owned by the United States and that the United States is an advanced country in the field of unmanned technology used in agriculture. The evaluation score of the important patents using the existing method was biased toward the PII index among the three patent evaluation standards, and the effects of the number of claims and the PFS were relatively small. Therefore, a reliable patent analysis in the field of unmanned technology used in agriculture needs to reflect the overall evaluation factors taking into consideration the scope of the evaluation factors.