Abstract: A relay unit includes a housing having a lower portion having four side faces each having an outlet; a heat exchanger accommodated in the housing; and a drain pan located below the heat exchanger. At a front face of the lower portion of the housing, a removable sheet metal cover having the outlet is formed. The drain pan includes a plate having four side portions, a side wall portion extending upward from each of the four side portions, and a drain socket provided in the side wall portion located forward or rearward, and to which a drain hose is connected. The drain pan is freely inserted and removed in a front-rear direction in a state in which the sheet metal cover is removed from the housing, and the drain pan is freely reversed front to rear to be accommodated in the housing.