To accurately detect a specific object and to stably trace the object.

A memory part 25 stores a reference pattern and a matching processing part 21 detects an area image that best matches the reference pattern from a photographed image. An extraction part 22 extracts the area image from the photographed image. When an integrated value of the differential absolute values of luminance values of corresponding pixels between the area image and the reference pattern is a fixed value and larger, a pattern obtained by correcting luminance so that the luminance values of respective pixels of the area image having the upper limit value or larger become the upper limit value of the differential absolute value is stored in the memory part 25 as a new reference pattern and update the reference pattern.