When focusing on quick movements in the analysis of animal behavior, a high-speed camera can be used as a powerful tool. There are many options for high-speed cameras to record movement. In recent years, the quality and sophistication of videos captured on cell phones have evolved so much that the iPhone’s slow-motion video system can function as a tool for behavior analysis. Here, we describe a method to analyze the movement of the ankle joint and jump speed during the jumping action of mice, using an iPhone.