An imaging device includes an imaging unit to obtain a captured image of a test pattern and a reference mark to locate the test pattern and at least one processor. The test pattern includes a pair of first marks and a second mark. The processor includes a position detector configured to detect the reference mark in the captured image and locate the pair of first marks and the second mark in the captured image, and a ratio calculator configured to calculate one of a first ratio between a distance between the pair of first marks in the captured image and a deviation of the second mark in the captured image, and a second ratio between the distance between the pair of first marks in the captured image and a distance from one of the pair of first marks to the second mark in the captured image.