—It is unclear whether affordance effects shorten the reaction time in the interaction between objects and actions. This study investigated affordance effects based on compatibility between perception of graspable objects and the act of grasping. The electromyographic reaction time (EMG-RT) was used as the response, and Go/NoGo (Experiment 1) and choice (Experiment 2) reaction-time tasks were performed using combinations of two types of stimulus image (tools and animals) and two types of response task (flexion and extension of all fingers). In Experiment 1, no interaction of stimulus images and response tasks occurred, but the EMG-RT for tools was statistically significantly delayed longer than that for animals. In Experiment 2, the EMG-RT of flexion of all fingers for tools was statistically significantly delayed compared with that for animals, showing interaction. Affordance effects based on compatibility of objects and actions are the basis on human-tool interaction. This interaction induces a goal-directed act and prolongs motor execution of grasping actions for them.