Indoor unit of air conditioner

The invention discloses an indoor unit of an air conditioner, which can enlarge the air supply breadth of an air outlet and improve the distribution uniformity of indoor temperature. The air conditioner indoor unit comprises a unit body and a panel, an air inlet and a plurality of main air outlets are formed in the panel, main air guide plates are arranged at the main air outlets in a rotary opening and closing mode, and air supply channels are formed between auxiliary air guide plates and the main air guide plates. The air supply channel is provided with an air supply channel first end close to the main air guide plate first end and an air supply channel second end away from the main air guide plate first end. Due to the fact that the air supply channel is narrower than an original air outlet, after air outlet air at the end of the main air outlet is blown out through the air supply channel, the air outlet air can be diffused towards the outer side of the end of the main air outlet in the length direction of