A heat pump apparatus comprising: a refrigerant circuit configured to circulate refrigerant; a heat medium circuit configured to make a heat medium flow; a heat exchanger configured to cause exchange heat to be performed between the refrigerant and the heat medium; an indoor unit having a housing corresponding to outer peripheral portions of the indoor unit and housing at least the heat exchanger; and a first duct and a second duct, the heat exchanger having a double-wall structure, the indoor unit including a container housed in the housing and housing the heat exchanger, wherein space in the container is isolated from space outside the container and in the housing, the container including a first opening port formed in the container and extending outwards from the housing, so that the space in the container communicates with space located outside the housing without communicating with the space located outside the container and in the housing, and a second opening port formed at a level different from that of the first opening port and extending outwards from the housing, so that the space in the container communicates with space located outside the housing without communicating with the space located outside the container and in the housing, the first opening port is configured to communicate with an outdoor space through the first duct so that the first opening port communicates with the outdoor space without communicating with an indoor space, and the second opening port is configured to communicate with the outdoor space through the second duct so that the second opening port communicates with the outdoor space without communicating with the indoor space. a refrigerant circuit configured to circulate refrigerant; a heat medium circuit configured to make a heat medium flow; a heat exchanger configured to cause exchange heat to be performed between the refrigerant and the heat medium; an indoor unit having a housing corresponding to outer peripheral portions of the indoor unit and housing at least the heat exchanger; and a first duct and a second duct, the heat exchanger having a double-wall structure, the indoor unit including a container housed in the housing and housing the heat exchanger, wherein space in the container is isolated from space outside the container and in the housing, the container including a first opening port formed in the container and extending outwards from the housing, so that the space in the container communicates with space located outside the housing without communicating with the space located outside the container and in the housing, and a second opening port formed at a level different from that of the first opening port and extending outwards from the housing, so that the space in the container communicates with space located outside the housing without communicating with the space located outside the container and in the housing, the first opening port is configured to communicate with an outdoor space through the first duct so that the first opening port communicates with the outdoor space without communicating with an indoor space, and the second opening port is configured to communicate with the outdoor space through the second duct so that the second opening port communicates with the outdoor space without communicating with the indoor space.