A heat exchanger for an indoor unit of an air conditioner, including at least a housing (1) having an air inlet (15) and an air outlet (16), a cooling coil (3), and a centrifugal blower (4) having an air exit (17), a volute housing (5), a motor (6) and a centrifugal wind wheel (7). The cooling coil (3) and the centrifugal blower (4) are disposed in the housing (1). The air inlet (15) and the air outlet (16) are disposed on both ends of the housing (1). The cooling coil (3) is disposed at the back of the air inlet (15). The centrifugal blower (4) is disposed at the back of the cooling coil (3). The air exit (17) of the centrifugal blower (4) is connected to the air outlet (16) of the housing (1). The motor (6) is an external rotor motor and fits in the center of a cavity in the centrifugal wind wheel (7). A left air intake (11) and a right air intake (12) are formed on both sides of the volute housing (5). The heat exchanger features large air input and air output, and high blowing efficiency.