In an indoor unit of an air-conditioning apparatus, an air inlet for room air is provided at a position lower than a height position of a drain pan. A partition plate is provided to partition a space below a height position of the drain pan in a housing. A pipe connecting portion connected to a refrigerant pipe of an outdoor unit is provided in one part of the partitioned space and a heat exchanger and a fan are placed in the other part of the partitioned space. At least one communicating path is formed in the partition plate to communicate the two parts of the partitioned space with each other. The indoor unit can include a controller for activating a fan when leakage of refrigerant is detected or for closing the communicating path when leakage of refrigerant is detected.