For use in calibration of an onboard camera, there are provided a calibration index free of erroneous detection and a method of calibrating an onboard camera using such calibration index. The calibration index for use in onboard camera calibration includes a curved graphic formed of a curved line surrounding a predetermined region and a linear graphic comprising at least two straight lines forming an intersection point within the region surrounded by the curved graphic, the curved graphic and the linear graphic being formed in a same plane. A plurality of segments separated by the curved line forming the curved graphic and the straight lines forming the linear graphic are colored in a checkered pattern.