1. An image processing apparatus comprising: a degree-of-relevance calculation unit configured to calculate a degree of relevance between a plurality of images based upon at least one item selected from a group consisted of a person's face captured in the images, determination results of scenes and objects in the images, GPS information of the images, and a degree of similarity of the images; an important image extraction unit configured to extract images captured over a certain period of time including a reference date for determining a degree of importance of the image, and images captured over a certain period of time including a relevant date relevant to the reference date, as important images, from the plurality of images; an instruction input unit configured to receive various instructions input by a user; and a relevant image extraction unit configured to extract a certain number of images, as relevant images, from the important images of which the degree of relevance to a selected image selected from the plurality of images by the instruction input through the instruction input unit is equal to or greater than a threshold.