Disclosed are an environmental test chamber having a movable panel and a method of driving the same. The environmental test chamber is used in a thermo-hygrostat, a thermostat, and a high temperature-low temperature tester. The chamber body includes a test cavity in which an object is disposed. An air-conditioning unit conditions the air inside the test cavity, thereby controlling a condition of the test cavity. A movable panel is accommodated in the chamber body to decrease or increase a volume of the test cavity. The efficiency of the chamber is enhanced, and the cost and space required for installing additional equipment is reduced.