The present disclosure relates to a clothes treating apparatus having a hot air supply device and an operating method thereof, and according to an aspect of the present disclosure, a clothes treating apparatus may include a drum configured to accommodate an object to be dried; a linear valve configured to linearly adjust the amount of supplied gas; a burner configured to burn gas supplied by the linear valve; a hot air supply device configured to supply hot air heated by the burner into the drum; a temperature sensor configured to measure the temperature of air exhausted from the drum; and a control means configured to adjust the amount of gas supplied to the burner based on a temperature measured by the temperature sensor, wherein the control means partitions a drying process into a plurality of sections based on a temperature change of the exhaust air, and varies a gas supply amount for each section.