Thermal processing apparatus and thermal processing method

An upper plate on which a substrate is placed is cooled or heated by a thermal processor. The temperature of the thermal processor is adjusted by a temperature adjuster. The temperature of the upper plate is detected. A control value that is to be applied to the temperature adjuster in order to maintain the temperature of the upper plate at a set value is calculated as a control arithmetic value on the basis of the detected temperature. When the control arithmetic value decreases to a value less than a second threshold value, a first control that applies the control arithmetic value to the temperature adjuster is performed. When the control arithmetic value increases to a value not less than a first threshold value, a second control that applies a control set value higher than the control arithmetic value to the temperature adjuster is performed.