1. An image retrieval apparatus, comprising: an extraction unit configured to extract a local feature amount, which is a localized feature amount, from an input image; a retrieval unit configured to calculate a local feature similarity, which is a similarity between the extracted local feature amount and a local feature amount of each image registered in an image feature database, and acquire a plurality of candidate images based on the calculated local feature similarity; a parameter calculation unit configured to calculate a geometric transformation parameter between each candidate image and the input image using the extracted local feature amount; a determination unit configured to determine a calculation region on the input image corresponding to a global feature amount calculation region calculated in advance with respect to each candidate image, using the geometric transformation parameter; a feature amount calculation unit configured to calculate a global feature amount in the calculation region determined by the determination unit; a similarity calculation unit configured to calculate a similarity between each candidate image and the input image by comparing the global feature amount of each candidate image and the global feature amount of the input image; and an output unit configured to output each candidate image in order of similarity.