According to one embodiment, q substrate treatment device includes a placement stand, a plurality of support portions, a cooling part, a liquid supplier, and at least one protrusion. The placement stand has a plate shape, and is configured to rotate. The support portions are provided on one surface of the placement stand and configured to support a substrate. The cooling part is configured to supply a cooling gas into a space between the placement stand and a back surface of the substrate supported by the support portions. The liquid supplier is configured to supply a liquid onto a surface of the substrate. At least one protrusion is provided on the one surface of the placement stand and extends along a boundary line of a region where the substrate is provided in a plan view.