A cooking appliance for cooking food, comprising: a main body having a cooking chamber formed therein; a lower space portion formed inside the main body and configured to form a space separated from the cooking chamber between a bottom of the main body and the cooking chamber; and a lower heating unit installed inside the lower space portion, wherein the lower heating unit includes: a lower heater configured to generate heat; and a lower case having the lower heating unit installed therein and being slidably insertable into the lower space portion through the opening portion; wherein an opening portion connecting the lower space portion to a space inside of the main body is formed in the lower space portion between the bottom of the main body and the cooking chamber, and wherein the lower heating unit is inserted into or withdrawn from the lower space portion through the opening portion; characterized in that the main body includes: a rear surface unit defining a rear boundary surface of the cooking chamber; a lower surface unit defining a lower boundary surface of the cooking chamber; and a side surface unit defining a side boundary surface of the cooking chamber, wherein the lower surface unit is integrally formed to be connected to at least one of the rear surface unit and the side surface unit and partitions the cooking chamber and the lower space portion; wherein the lower case includes: a bottom surface unit forming a bottom surface of the lower case; a side wall unit extending upward from the bottom surface unit to form a side surface of the lower case; and a first discharge port (a) forming a discharge path in the side wall unit of the lower case; a second discharge port (b) formed in the side surface unit to form a path into an inside of the cooking chamber, wherein the cooking appliance further includes a flow path connection member (330, 330a) to form a flow path guide (c) connecting the first discharge port (a) and the second discharge port (b). a main body having a cooking chamber formed therein; a lower space portion formed inside the main body and configured to form a space separated from the cooking chamber between a bottom of the main body and the cooking chamber; and a lower heater configured to generate heat; and a lower case having the lower heating unit installed therein and being slidably insertable into the lower space portion through the opening portion; wherein an opening portion connecting the lower space portion to a space inside of the main body is formed in the lower space portion between the bottom of the main body and the cooking chamber, and wherein the lower heating unit is inserted into or withdrawn from the lower space portion through the opening portion; characterized in that the main body includes: a rear surface unit defining a rear boundary surface of the cooking chamber; a lower surface unit defining a lower boundary surface of the cooking chamber; and a side surface unit defining a side boundary surface of the cooking chamber, wherein the lower surface unit is integrally formed to be connected to at least one of the rear surface unit and the side surface unit and partitions the cooking chamber and the lower space portion; wherein the lower case includes: a bottom surface unit forming a bottom surface of the lower case; a side wall unit extending upward from the bottom surface unit to form a side surface of the lower case; and a first discharge port (a) forming a discharge path in the side wall unit of the lower case; a second discharge port (b) formed in the side surface unit to form a path into an inside of the cooking chamber, wherein the cooking appliance further includes a flow path connection member (330, 330a) to form a flow path guide (c) connecting the first discharge port (a) and the second discharge port (b). a rear surface unit defining a rear boundary surface of the cooking chamber; a lower surface unit defining a lower boundary surface of the cooking chamber; and a side surface unit defining a side boundary surface of the cooking chamber, wherein the lower surface unit is integrally formed to be connected to at least one of the rear surface unit and the side surface unit and partitions the cooking chamber and the lower space portion; a bottom surface unit forming a bottom surface of the lower case; a side wall unit extending upward from the bottom surface unit to form a side surface of the lower case; and a first discharge port (a) forming a discharge path in the side wall unit of the lower case; a second discharge port (b) formed in the side surface unit to form a path into an inside of the cooking chamber, wherein the cooking appliance further includes a flow path connection member (330, 330a) to form a flow path guide (c) connecting the first discharge port (a) and the second discharge port (b).