A clothes treatment apparatus comprising: a cabinet partitioned into a treatment chamber for allowing clothes to be hung therein; a cycle chamber for allowing machinery to be installed therein, and a tank installation space configured to allow a water supply tank and a drainage tank to be installed therein; a door for opening and closing the cabinet; a steam unit disposed in the cycle chamber for supplying steam into the treatment chamber; a heat pump unit disposed in the cycle chamber for circulating air in the treatment chamber and conditioning the air that is circulated; and a tank support bar defining a part of one surface of the tank installation space and configured for the water supply tank and the drainage tank to be placed thereon; wherein the water supply tank is separably installed in the tank installation space, and is connected to the steam unit configured to supply water to the steam unit, wherein the drainage tank is separably installed in the tank installation space, and is configured to store condensed water generated in at least one selected from between the treatment chamber and the heat pump unit, and wherein each of the water supply tank and the drainage tank includes a tank support end disposed at each bottom side outward vertically, characterized in that each tank support end is placed on the upper side of the tank support bar and interferes with the tank support bar when each of the water supply tank and the drainage tank is separably installed in the tank installation space to prevent the each of the water supply tank and the drainage tank from being unintentionally separated from the tank installation space. a cabinet partitioned into a treatment chamber for allowing clothes to be hung therein; a cycle chamber for allowing machinery to be installed therein, and a tank installation space configured to allow a water supply tank and a drainage tank to be installed therein; a door for opening and closing the cabinet; a steam unit disposed in the cycle chamber for supplying steam into the treatment chamber; a heat pump unit disposed in the cycle chamber for circulating air in the treatment chamber and conditioning the air that is circulated; and a tank support bar defining a part of one surface of the tank installation space and configured for the water supply tank and the drainage tank to be placed thereon; wherein the water supply tank is separably installed in the tank installation space, and is connected to the steam unit configured to supply water to the steam unit, wherein the drainage tank is separably installed in the tank installation space, and is configured to store condensed water generated in at least one selected from between the treatment chamber and the heat pump unit, and wherein each of the water supply tank and the drainage tank includes a tank support end disposed at each bottom side outward vertically, characterized in that each tank support end is placed on the upper side of the tank support bar and interferes with the tank support bar when each of the water supply tank and the drainage tank is separably installed in the tank installation space to prevent the each of the water supply tank and the drainage tank from being unintentionally separated from the tank installation space.