Substrate treatment device

A substrate treatment device, comprising:

• a placement stand configured to rotate a substrate;
• a cooling part configured to supply a cooling gas into a space between the placement stand and the substrate;
• a liquid supplier configured to supply a liquid on a surface of the substrate opposite to the placement stand side;
• a detector configured to detect a state of the liquid on the surface of the substrate;
• and
• a controller controlling at least one of a rotation speed of the substrate, a flow rate of the cooling gas, or a supply amount of the liquid,
• the controller setting the liquid on the surface of the substrate to be in a supercooled state, obtaining a temperature of the liquid in the supercooled state at a start of freezing based on data from the detector, and being configured to calculate a removal ratio of a contamination from a relationship between a temperature at the start of freezing obtained in advance and a removal ratio of the contamination, and the temperature at the start of freezing based on data from the detector.