An ozone flow rate control device for controlling a flow rate of ozone gas supply, according to the present invention, comprises an inlet pipe to which the ozone gas is supplied, a bypass pipe and a sensor pipe branched from the inlet pipe, a control signal generator circuit for measuring a variation of temperature of the sensor pipe and generating a control signal corresponding to a flow rate of the ozone gas, an outlet pipe connected to the bypass pipe and the sensor pipe, a valve provided in the outlet pipe and having an opening controlled correspondingly to the control signal and heating means for heating the ozone gas supplied to the sensor pipe to a predetermined temperature.