An indoor unit configured to be connected to an outdoor unit, the indoor unit comprising: a heat exchanger unit; and a fan to generate an air flow, wherein the heat exchanger unit includes: a first heat exchanger including a first header and a second header, and a first flat pipe group that includes a plurality of flat multi-hole pipes connected to each of the first header and the second header; and a second heat exchanger arranged in parallel with the first heat exchanger and disposed on an air downstream side, from the first heat exchanger, of the air flow generated by the fan, the second heat exchanger including a third header and a fourth header, and a second flat pipe group that includes a plurality of flat multi-hole pipes connected to each of the third header and the fourth header, wherein, in the first flat pipe group, the plurality of flat multi-hole pipes are arranged in an up-down direction, one or more of the flat multi-hole pipes on an upper side form an upper-side first heat exchanging region, and one or more of the flat multi-hole pipes on a lower side form a lower-side first heat exchanging region, wherein the first header includes an upper-side first header and a lower-side first header that are respectively connected to the flat multi-hole pipes of the upper-side first heat exchanging region and the flat multi-hole pipes of the lower-side first heat exchanging region, and wherein the fourth header causes a refrigerant that flows in from the third header to flow out to the lower-side first header, wherein the second header includes an upper-side second header and a lower-side second header that are respectively connected to the flat multi-hole pipes of the upper-side first heat exchanging region and the flat multi-hole pipes of the lower-side first heat exchanging region, a gas-refrigerant pipe configured to receive a gaseous refrigerant from the outdoor unit, and a liquid-refrigerant pipe configured to send a liquid refrigerant to the outdoor unit, characterized in that the fourth header causes the gaseous refrigerant that flows in from the third header to flow out of the first header, an area of the upper-side first heat exchanging region is larger than an area of the lower-side first heat exchanging region, and the gas-refrigerant pipe is further connected to the upper-side first header and the third header, and the liquid-refrigerant pipe is individually connected to the upper-side second header and the lower-side second header. a heat exchanger unit; and a fan to generate an air flow, wherein the heat exchanger unit includes: a first heat exchanger including a first header and a second header, and a first flat pipe group that includes a plurality of flat multi-hole pipes connected to each of the first header and the second header; and a second heat exchanger arranged in parallel with the first heat exchanger and disposed on an air downstream side, from the first heat exchanger, of the air flow generated by the fan, the second heat exchanger including a third header and a fourth header, and a second flat pipe group that includes a plurality of flat multi-hole pipes connected to each of the third header and the fourth header, a first heat exchanger including a first header and a second header, and a first flat pipe group that includes a plurality of flat multi-hole pipes connected to each of the first header and the second header; and a second heat exchanger arranged in parallel with the first heat exchanger and disposed on an air downstream side, from the first heat exchanger, of the air flow generated by the fan, the second heat exchanger including a third header and a fourth header, and a second flat pipe group that includes a plurality of flat multi-hole pipes connected to each of the third header and the fourth header, wherein, in the first flat pipe group, the plurality of flat multi-hole pipes are arranged in an up-down direction, one or more of the flat multi-hole pipes on an upper side form an upper-side first heat exchanging region, and one or more of the flat multi-hole pipes on a lower side form a lower-side first heat exchanging region, wherein the first header includes an upper-side first header and a lower-side first header that are respectively connected to the flat multi-hole pipes of the upper-side first heat exchanging region and the flat multi-hole pipes of the lower-side first heat exchanging region, and wherein the fourth header causes a refrigerant that flows in from the third header to flow out to the lower-side first header, wherein the second header includes an upper-side second header and a lower-side second header that are respectively connected to the flat multi-hole pipes of the upper-side first heat exchanging region and the flat multi-hole pipes of the lower-side first heat exchanging region, a gas-refrigerant pipe configured to receive a gaseous refrigerant from the outdoor unit, and a liquid-refrigerant pipe configured to send a liquid refrigerant to the outdoor unit, characterized in that the fourth header causes the gaseous refrigerant that flows in from the third header to flow out of the first header, an area of the upper-side first heat exchanging region is larger than an area of the lower-side first heat exchanging region, and the gas-refrigerant pipe is further connected to the upper-side first header and the third header, and the liquid-refrigerant pipe is individually connected to the upper-side second header and the lower-side second header.