When operating an automotive human-machine interface (HMI) device while driving,the driver moves his/her eyes to the operating device and the display. In order to use the HMI without distracting from the main driving operation, it is important to minimize the visual workload of the secondary HMI task. The purpose of this study is to investigate the influence of instrument panel design on the driver’s visibility and usability of the HMI device. Our driving evaluation suggests that instrument panel decoration affects the driver’s performance of HMI manipulation. Specifically, manipulation speed and the detection accuracy of a target in the peripheral vision were improved when the most salient line of the instrument panel was orthogonal to the optical flow of the roadway in the windshield. Moreover, the color of the panel also affected the performance. These results indicate that a well-designed instrument panel can reduce visual workload of the secondary HMI task by improving visibility of the HMI device. Application of this finding to the current instrument panel design is illustrated.