The present invention provides an indoor unit of an air conditioner, which is capable of improving the mounting accuracy between a front grill and a movable panel. An indoor unit of the air conditioner includes a main body casing, a front grill, a second panel, a driving machine, and an opening and closing mechanism. The front grill is provided forward of the main body casing and includes a first intake port. The second panel is capable of moving so as to open and close the first intake port. The driving machine is provided in the main body casing, and generates a driving force to move the second panel. The opening and closing mechanism is provided at the front grill, and moves the second panel by the driving force of the driving machine to open and close the first intake port.