A substrate treatment device includes: a substrate rotation part that horizontally holds and rotates a substrate; a nozzle that supplies a treatment liquid to a surface to be treated of the substrate rotated by the substrate rotation part; an imaging part that captures an image of an imaging area including a plurality of target areas in which a liquid film is formed when the treatment liquid is supplied to the substrate; and a detection part that refers to an imaging result of the imaging part and detects a treatment ending time point of each of the target areas based on a change in luminance value for each of the target areas. Further, the imaging area includes at least an area on a center side of the surface to be treated and an area on an outer circumferential side of the surface to be treated as the target areas.