A three-dimensional position estimation device includes: a feature point extracting unit for detecting an area corresponding to the face of an occupant in an image captured by a camera for imaging a vehicle interior and extracting a plurality of feature points in the detected area; an inter-feature-point distance calculating unit for calculating a first inter-feature-point distance that is a distance between distance-calculating feature points among the plurality of feature points; a face direction detecting unit for detecting the face direction of the occupant; a head position angle calculating unit for calculating a head position angle indicating the position of the head of the occupant with respect to an imaging axis of the camera; an inter-feature-point distance correcting unit for correcting the first inter-feature-point distance to a second inter-feature-point distance that is a distance between distance-calculating feature points in a state where portions of the head corresponding to the distance-calculating feature points are arranged along a plane parallel to an imaging plane of the camera using a result detected by the face direction detecting unit and the head position angle; and a three-dimensional position estimating unit for estimating the three-dimensional position of the head using the head position angle, the second inter-feature-point distance, and a reference inter-feature-point distance.