Abstract: A plasma processing apparatus having an improved yield includes a metal base member having a disk shape or a cylindrical shape arranged inside a sample table; a refrigerant flow path arranged multiple times in a concentrical shape around a center of the base member; at least one temperature sensor; and a controller configured to detect a temperature of the base member or the wafer using the temperature sensor. The controller is configured to detect the temperature of the base member or the wafer based on one of a plurality of linear functions indicating a relation between an error and a set temperature of the refrigerant, and the linear functions are different corresponding to regions of a plurality of continuous temperature ranges within an adjustable temperature range of the refrigerant, and the plurality of linear functions include the same coefficient and have a point where the error is 0.