To enhance responsiveness to a change in an air quantity, and prevent a temperature from becoming an abnormal high temperature by arranging an air quantity detecting means to detect an air quantity from an air blower in wind tunnel, and controlling current-carrying to a heater by its detecting signal.

A thin plate body 8a to constitute an air quantity detecting means 8 arranged on the delivery side of an air blower 6 is deformed according to the size of wind pressure from the air blower 6, and this is detected by a strain gauge, and when its detecting signal is sent to a control part 9, the control part 9 controls current-carrying of a heater 10 on the basis of its detecting signal. In this way, when an electric current is carried to the heater 10 after an air quantity is detected at starting time, responsiveness to a change in an air quantity is remarkably enhanced. In a hot air device 1, a suction port 3 is arranged on one end side of a housing 2 formed in a cylindrical shape, and a delivery port 4 is arranged on the other end side, and a cylindrical wind tunnel 5 to communicate with the suction port 3 and the delivery port 4 are formed inside the housing 2.