Provided is a user interface device (10) that estimates a user's degree of interest, for performing an input process on the basis of the user's degree of interest in a plurality of objects displayed on a screen (26). The device includes a gaze direction detection unit (11) that detects a gaze direction of the user; a gaze duration calculation unit (12) that calculates gaze duration during which the gaze direction has remained on each of the plurality of objects; an eye-attracting force calculation unit (13) that calculates eye-attracting force of each of the plurality of objects; and a degree of interest estimation unit (14) that estimates the user's degree of interest in each of the plurality of objects, such that the longer the gaze duration is the higher the degree of interest becomes, and that the smaller the eye-attracting force is the higher the degree of interest becomes.