A ceiling mounted air conditioner comprising: an indoor unit having a built-in heat exchanger and a built-in blower and comprising a plurality of blowing passages (7, 8, 9, 10) configured to discharge air which passes through the heat exchanger to the outside; a discharge panel comprising a plurality of inlets (21, 22, 23, 24) receiving the air discharged through the plurality of blowing passages (7, 8, 9, 10), an inner space configured to at least partially communicate with the plurality of inlets (21, 22, 23, 24), and a ring-shaped or arc-shaped opening configured to discharge, to a room, air which flows into the inner space, wherein the discharge panel include a main flow path body and an inner flow path body coupled to the main flow path body; and an air guide module mounted on the discharge panel, wherein the air guide module is mounted at an end portion of the main flow path body or the inner flow path body; characterized in that: the air guide module comprises: at least one air guide disposed at the inner flow path body and configured to be lifted/lowered to vary a flow of the air discharged to the opening; wherein a surface of the air guide module which faces the inner space is configured as a flat surface to guide a horizontal air current when the air guide module is lifted, and wherein the air discharged through the opening is unaffected by the air guide module when the air guide module is lowered and is guided as a vertical air current, wherein an upper end of the air guide is the flat surface. an indoor unit having a built-in heat exchanger and a built-in blower and comprising a plurality of blowing passages (7, 8, 9, 10) configured to discharge air which passes through the heat exchanger to the outside; a discharge panel comprising a plurality of inlets (21, 22, 23, 24) receiving the air discharged through the plurality of blowing passages (7, 8, 9, 10), an inner space configured to at least partially communicate with the plurality of inlets (21, 22, 23, 24), and a ring-shaped or arc-shaped opening configured to discharge, to a room, air which flows into the inner space, wherein the discharge panel include a main flow path body and an inner flow path body coupled to the main flow path body; and an air guide module mounted on the discharge panel, wherein the air guide module is mounted at an end portion of the main flow path body or the inner flow path body; characterized in that: the air guide module comprises: at least one air guide disposed at the inner flow path body and configured to be lifted/lowered to vary a flow of the air discharged to the opening; wherein a surface of the air guide module which faces the inner space is configured as a flat surface to guide a horizontal air current when the air guide module is lifted, and wherein the air discharged through the opening is unaffected by the air guide module when the air guide module is lowered and is guided as a vertical air current, wherein an upper end of the air guide is the flat surface. the air guide module comprises: at least one air guide disposed at the inner flow path body and configured to be lifted/lowered to vary a flow of the air discharged to the opening; wherein a surface of the air guide module which faces the inner space is configured as a flat surface to guide a horizontal air current when the air guide module is lifted, and wherein the air discharged through the opening is unaffected by the air guide module when the air guide module is lowered and is guided as a vertical air current, wherein an upper end of the air guide is the flat surface.