The purpose of this paper is to identify the optimal levels of insider shareholding and R&D spending, as a means of alleviating conflicts between managers and shareholders. This study analyzed whether insider shareholding affected R&D spending, employing a panel of 252 Taiwanese listed electronics companies, over a decade (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) term. When insider shareholding was less than 13.84%, R&D spending decreased by 0.05386% for each 1% increase in insider shareholding; When insider shareholding was more than 13.84%, R&D spending increased by 0.0275% for each 1% increase in insider shareholding. These results suggest that insiders holding a big part of equity were controlled by ultimate controllers related to family conglomerates, who generally have an incentive to decide R&D spending up to the maximum value of stockholders.