1. A degree of interest estimating device which estimates a degree of interest of a user in a video displayed on a screen, the degree of interest estimating device comprising: a processor; and a non-transitory memory having stored thereon executable instructions, which when executed, cause the processor to perform: detecting an eye gaze direction of the user; obtaining saliency information on a saliency area having salient attractiveness in the video; calculating a correlation between the saliency area specified from the obtained saliency information and the detected eye gaze direction; and estimating the degree of interest of the user in the video, the degree of interest being higher as the calculated correlation is higher, wherein the obtaining the saliency information includes (i) determining saliency patterns based on a number of saliency areas in the video and a motion of one or more saliency areas including the saliency area, in each of a plurality of frames of the video, the saliency patterns classifying the one or more saliency areas as one of (a) a dynamic pattern indicating that the one or more saliency areas temporally change in position and (b) a static pattern indicating that the one or more saliency areas do not temporally change in position, (ii) temporally segmenting the video into video sequences based on the determined saliency patterns, and (iii) obtaining, as the saliency information, the saliency patterns corresponding to the video sequences, the calculating the correlation includes calculating, for each video sequence of the video sequences, the correlation using at least one of an evaluation criteria associated with the saliency pattern corresponding to the video sequence, such that the degree of interest of the user in the video is estimated with high accuracy, and the calculating the correlation includes calculating, as a value showing how low the correlation is, a speed difference between a moving speed of the saliency area on the screen and a moving speed of a gaze position on the screen specified from the eye gaze direction, and in the estimating the degree of interest, the degree of interest is estimated so that the degree of interest is higher as the speed difference is smaller.