SWOT and TOWS are acronyms for different arrangements of the words Strengths, Weaknesses, Opportunities and Threats. SWOT and TOWS analysis is used to identify and address internal and external issues faced by organizations. Even in this era of the Internet of Things in which huge amounts of information are constantly being exchanged, however, web-based SWOT and TOWS analytical tools that use information and communications technologies have not yet been developed. Also, there is no established method to promote new ideas by non-participants. Agriculture in Japan is facing major challenges, such as increasing numbers of abandoned farms and uncultivated areas due to the aging farming population and increased competition from global markets. To solve these problems and promote agriculture, various ideas that have not existed in the past are sought. This study developed iSWOT, a web-based SWOT and TOWS analytical tool that encourages brainstorming and the use of the KJ method (i.e., affinity diagrams). Previous studies have indicated that the interference effect prompts the generation of secondary ideas by enabling each participant’s ideas to influence those of others. Therefore, in order to promote new ideas, after classifying interference by participants as internal interference and categorizing the interference by outsiders as external interference, we implemented functions that exert the internal and external interference effect on iSWOT. Consequent to the functional test performed by farmers and agricultural extension workers, it has been confirmed the effectiveness of this tool to promote new ideas.