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, acquiring a plurality of captured images; extracting, from each of the plurality of captured images, a first feature amount and a second feature amount of a user included in the captured image, and a third feature amount indicating a condition of acquiring of the captured image; generating an authentication table including a plurality of templates, each of which corresponds to each of the plurality of the captured images, each of the templates including the first feature amount, the second feature amount, and the third feature amount extracted from each of the plurality of captured images; acquiring an authentication image of a target user; extracting the third feature amount from the authentication image of the target user; selecting a template among the plurality of the templates by comparing the third feature amount of the authentication image and a plurality of third feature amounts included in the authentication table; and authenticating the target user based on the first feature amount and the second feature amount which are included in the selected template, and the first feature amount and the second feature amount which are extracted from the authentication image.