1. An album generating apparatus, comprising: an image storing section for storing images; a layout determining section for laying out the images stored in said image storing section per page in the album; and a main image selecting section for selecting one of the images that are laid out in a predetermined page of the album by said layout determining section as a main image of the predetermined page, wherein said image storing section stores a preliminary image captured in succession before or after each of the images laid out in the predetermined page, said album generating apparatus further comprising: an object sampling section for detecting objects contained within the images laid out in the predetermined page; and a momentum calculating section for calculating a momentum indicating a scale of motion of an object detected by said object sampling section based on one of the images laid out in the predetermined page which contains the detected object and the corresponding preliminary image, wherein said main image selecting section selects as the main image, one of the images laid out in the predetermined page which contains an object detected by said object sampling section that has a large scale of motion according to the momentum calculated by said momentum calculating section.