A clothes treating apparatus including a drum, an air suction duct forming a flow path of air introduced into the drum, an auxiliary fan introducing air into the air suction duct, an air exhaustion duct forming a flow path of air exhausted from the drum, a main fan exhausting air to the air exhaustion duct from the drum, a condenser heating air sucked into the drum through the air suction duct, an
evaporator cooling air exhausted from the drum through the air exhaustion duct, and a compressor and an expander forming a
heat pump together with the condenser and the
evaporator. The method includes measuring a
discharge side pressure of the compressor, and comparing the measured
discharge side pressure with a maximum allowable pressure, and determining that the auxiliary fan does not operate when the
discharge side pressure is more than the maximum allowable pressure.