1. An image extraction device, comprising: an instruction acquisition unit that acquires an instruction input by a user; an image group selection unit that selects a second image group, which has a smaller number of images than a first image group, from the first image group in response to the instruction; an extraction reference determination unit that determines an image extraction reference when extracting an image from the second image group based on images included in the first image group; an image extraction unit that extracts one or more images, the number of which is smaller than the number of images in the second image group, from the second image group according to the image extraction reference; and an image analysis unit that analyzes images included in the first image group and calculates a relationship between persons present in the images included in the first image group based on the analysis result; the image analysis unit comprising: an image information acquisition section that acquires image information regarding images included in the first image group; an image feature analysis section that analyzes features of the images included in the first image group based on the image information; and a relationship calculation section that calculates a relationship between persons present in the images included in the first image group based on the image information and the image feature, wherein the extraction reference determination unit determines the image extraction reference according to the relationship between persons, the relationship calculation section determines a degree of importance of each person from the relationship between persons, the extraction reference determination unit determines the image extraction reference according to the degree of importance of each person, the relationship calculation section determines one or more persons whose number of times of appearance is equal to or greater than a threshold value in the first image group, among persons present in the images included in the first image group, as main persons, and determines one or more persons who are present in the images included in the first image group and whose distances from the main persons are equal to or less than a threshold value, among persons other than the main persons who are present in the images included in the first image group, as important persons, and the extraction reference determination unit determines the image extraction reference according to the main persons and the important persons.