An air purifying robot and its operation method capable of purifying air using a mobile robot are disclosed. To this end, an air purifying robot comprises: a main body casing having a certain space therein, and provided with a suction hole for sucking ambient air and a discharge hole for discharging the purified air; a fan motor installed in the main body casing, and rotating so as to suck the ambient air of the main body casing through the suction hole; a dust collecting filter for filtering pollutants contained in the ambient air having been sucked through the suction hole; main wheels installed at a lower surface of the main body casing at a certain interval therebetween, and driven by the motor; an auxiliary wheel installed so as to maintain a horizontal state of the main casing, and moving the air purifying robot together with the main wheels; and a control unit for controlling the fan motor, the dust collecting filter and the main wheels.