An air handling unit comprising: a base to support a weight of each of a plurality of modules (100, 200, 300, 400); a plurality of module frames installed on the base to define an external appearance of the module having a prescribed shape, each of the module frames having one or more sliding ribs (21', 21") protruding outward in a direction perpendicular to a longitudinal direction of the module frames; a plurality of connectors to interconnect the plurality of module frames; and a plurality of case panels coupled to the module frames to form surfaces of the module, the case panels comprising sliding rail grooves formed in rims thereof such that the sliding ribs (21', 21") are fitted into the sliding rail grooves, wherein the case panels have: a lower cover forming a lower surface of the module; a side cover forming a side surface of the module; an upper cover forming an upper surface of the module; and a middle frame; and a separation partition configured to divide an inner space of a module (100, 400) into a suction chamber for introduction of air at one side thereof and a centrifugal chamber at the other side thereof, the centrifugal chamber accommodating a fan module (101; 401) configured to generate airflow power, the separation partition having a communication opening for communication between the suction chamber and the centrifugal chamber; wherein the separation partition, being one of the panels, is slidably coupled to the middle frame in the same manner as the other panels having both ends slidably inserted in a vertical direction to the module frames forming the framework of the module so as to divide the inner space of the module into the suction chamber and the centrifugal chamber arranged in sequence in a flow direction of the air. a base to support a weight of each of a plurality of modules (100, 200, 300, 400); a plurality of module frames installed on the base to define an external appearance of the module having a prescribed shape, each of the module frames having one or more sliding ribs (21', 21") protruding outward in a direction perpendicular to a longitudinal direction of the module frames; a plurality of connectors to interconnect the plurality of module frames; and a plurality of case panels coupled to the module frames to form surfaces of the module, the case panels comprising sliding rail grooves formed in rims thereof such that the sliding ribs (21', 21") are fitted into the sliding rail grooves, wherein the case panels have: a lower cover forming a lower surface of the module; a side cover forming a side surface of the module; an upper cover forming an upper surface of the module; and a middle frame; and a separation partition configured to divide an inner space of a module (100, 400) into a suction chamber for introduction of air at one side thereof and a centrifugal chamber at the other side thereof, the centrifugal chamber accommodating a fan module (101; 401) configured to generate airflow power, the separation partition having a communication opening for communication between the suction chamber and the centrifugal chamber; wherein the separation partition, being one of the panels, is slidably coupled to the middle frame in the same manner as the other panels having both ends slidably inserted in a vertical direction to the module frames forming the framework of the module so as to divide the inner space of the module into the suction chamber and the centrifugal chamber arranged in sequence in a flow direction of the air. a lower cover forming a lower surface of the module; a side cover forming a side surface of the module; an upper cover forming an upper surface of the module; and a middle frame; and a separation partition configured to divide an inner space of a module (100, 400) into a suction chamber for introduction of air at one side thereof and a centrifugal chamber at the other side thereof, the centrifugal chamber accommodating a fan module (101; 401) configured to generate airflow power, the separation partition having a communication opening for communication between the suction chamber and the centrifugal chamber; wherein the separation partition, being one of the panels, is slidably coupled to the middle frame in the same manner as the other panels having both ends slidably inserted in a vertical direction to the module frames forming the framework of the module so as to divide the inner space of the module into the suction chamber and the centrifugal chamber arranged in sequence in a flow direction of the air.