1. An image processing device comprising: a processor; and a memory which stores a plurality of instructions, which when executed by the processor, cause the processor to execute: determining whether or not an eye region of a user being detected a line-of-sight in an image resulting from photographing an eye of the user is influenced by reflection light, the eye region being a region of the eye; and detecting, as a feature portion of the eye, a region that is included in the eye region and that includes a pixel having a feature that is the same as or similar to any of features of the feature portion, when it is determined that the eye region is influenced by the reflection light, the features being accumulated for respective strengths of influences of the reflection light that appear in images of the feature portion of the eye.