PURPOSE: To prevent the occurrence of a trouble wherein the mounting place of a flow rate regulation dial is limited to the vicinity of a cock by providing a control device to control the voltage of a motor for driving a pump when a flow rate of liquid is controlled by a pump driven by a DC motor.

CONSTITUTION: Liquid, such as water, is sprayed against a belt 18 made of cloth through a pipe 19 with small holes in which a number of small holes are disposed, air is cooled by the heat of vaporization of impregnating water and cold air is generated through operation of a fan 20. A discharge port 4 consisting of a pipe connected to a liquid tank 1 is connected to the pipe 19 with small holes of a so formed cold air generating device, and a pump 2 to which a liquid flow rate control device is applicable is connected to the pipe. By controlling the voltage of a motor 12 to drive the pump 2 by a control device 14, a flow rate of liquid is controlled. The control device 14 is formed in such a manner that a control panel is provided with an output voltage set volume to which a flow rate regulating dial is attached and an ON-OFF switch.