PURPOSE: To measure the temperature distribution of a substrate by forming thin- film thermocouples on the substrate and by detecting the temperature of the substrate by switching those thin-film thermocouples successively.

CONSTITUTION: On an insulation-treated substrate 1, thin-film thermocouples 2aW 2n are formed, and compensating conductors 6aW6n, and 7aW7n are connected to the thermocouples 2aW2n respectively; and those compensating conductors 6aW7n are connected to changeover switches 8 and 9, the other terminals of which are connected to a potentiometer 10. Further, a controller 13 is equipped to control the changeover switches 8 and 9 and potentiometer 10. Then, the controller 13 switches the changeover contacts 8aW8n, and 9aW9n of the switches 8 and 9 to select the thermocouples 2aW2n successively, thereby detecting the temperature of the substate at more than one point.