An ECU of a night vision system stores small obtained images of provisional targets as six templates depending on the distance from infrared cameras, and selects one of the templates depending on the distance up to an actual object. Using the selected template, the ECU performs template matching on images obtained by the infrared cameras, and calculates coordinates of the inspection target. The ECU compares the calculated coordinates of the inspection target and stored reference coordinates with each other, and determines mounted angles of the infrared cameras.