evaporation section accordingly even when the amount of supplied heat is reduced it is taken into consideration that it does not have a significant effect during the drying time furthermore the saving course temporarily cuts off gas supply during the second heating section it is to prevent an excessive temperature increase and it may be also possible to maintain the gas supply amount at a constant level when the temperature increase rate is small the following table 1 summarizes the fuel consumption amount and drying time consumed during the conventional course rapid course and saving course here the initial percentage of water content for the laundry put therein is 70 and the weight thereof is 3 714 kg as illustrated in the above table 1 it is seen that both the two courses in the foregoing embodiment use a smaller amount of gas and complete the drying process within a shorter period of time compared to the related art on the other hand the weight of the laundry put therein may be indirectly measured through a gradient in the first heating section even without using an additional weight sensor in other words when it is assumed that the same amount of heat is supplied the temperature increase rate is smaller as increasing the amount of the laundry put therein and thus a gradient in the first heating section will be reduced as a graph illustrated in fig6 accordingly when a reference value is determined in advance it may be possible to determine.