An AR image generator 526 employs, as a marker, a subject imaged by an imaging element that images the subject existing in a region including the field of view of a user who wears an optically transmissive HMD and is provided for the optically transmissive HMD, and generates an AR image to be presented by the optically transmissive HMD. A proximity acquirer 560 acquires the distance in a virtual three-dimensional space between a first AR image associated with a first marker and a second marker or a second AR image associated with the second marker. An interaction producer 570 calculates an interaction caused with the first AR image or the second AR image based on the distance acquired by the proximity acquirer 560. The AR image generator 526 changes at least either one image of the first AR image or the second AR image according to the interaction calculated by the interaction producer 570.