To provide a uniform heating method for heating a platy sample easily with uniform distribution of temperatures without receiving an influence from a temperature distribution of a partition wall.

In the method in which a circular platy sample 5 is heated uniformly at temperatures through a transparent separation wall 2 with a lamp 3, a transparent partition wall 2 has a recessed part 7 and the platy sample is mounted on the recessed part 7. The platy sample 5 is heated with a plurality of circular lamps. After the temperature of the platy sample becomes constant, a difference in temperature between the circumferential part and the central part of the flat face of the platy sample is detected. The power ratio of the lamps is adjusted to cancel the difference in the temperature.