The invention relates to an indoor machine of an air conditioner, which comprises a casing, a front panel, a heat exchanger, a defrosting tray, a fan, an air inlet, an air outlet and an air passage, wherein the front panel is installed at the front part of the casing, the heat exchanger, the defrosting tray and the fan are installed in a cavity body formed by the casing and the front panel, the air passage is arranged in the cavity body formed by the casing and the front panel, the fan is installed in the air passage, the air outlet is arranged on the casing or the front panel, and the position of the air outlet is provided with an air-supply air deflector. The indoor machine of the air conditioner is characterized in that the air inlet is arranged at the upper part of the front panel. On the basis of the structure of the indoor machine of a traditional wall-hanging type air conditioner, the invention moves the air inlet from the top of the casing to the upper part of the front panel. By the structural design, air does not need to enter the indoor machine of the air conditioner from the top any more, so that the indoor machine of the air conditioner can be hung and installed on a ceiling or embedded in a wall or furniture and can adapt to more installation spaces and positions.