A cooking appliance comprising: a cavity to provide a cooking chamber; a door to open and close the cooking chamber; a partition plate to partition the cavity into a first chamber and second chamber, the partition plate facing the door in the closed state, wherein the door closes the first chamber; and a burner assembly disposed in the second chamber to supply heated air into the first chamber, wherein the burner assembly comprises: a burner cover (130, 630, 730) to partition the second chamber into a combustion chamber and an exhaust chamber, a burner disposed in the combustion chamber for burning gas to generate flame, a fan disposed in the exhaust chamber, and a nozzle holder disposed outside a rear wall of the cavity, the nozzle holder having a gas spraying hole to spray the gas into the burner, the burner comprises a supply part to receive gas and air, the supply part passing through the rear wall of the cavity, wherein the supply part comprises a plurality of first guides (121, 122) to align the supply part with the gas spraying hole, the plurality of first guides (121, 122) being spaced apart from each other; wherein the nozzle holder comprises a plurality of second guides (224, 225) to guide the plurality of first guides (121, 122) of the supply part, wherein the nozzle holder has an accommodation groove in which the plurality of first guides (121, 122) is accommodated, and the plurality of first guides (121, 122) contacts the plurality of second guides (224, 225) in the state where the plurality of first guides (121, 122) is accommodated into the accommodation groove, wherein the accommodation groove is disposed between the plurality of second guides (224, 225) of the nozzle holder, and wherein the plurality of first guides (121, 122) of the supply part is accommodated into the accommodation groove of the nozzle holder in the state where the plurality of first guides (121, 122) is disposed between the plurality of second guides (224, 225) of the nozzle holder. a cavity to provide a cooking chamber; a door to open and close the cooking chamber; a partition plate to partition the cavity into a first chamber and second chamber, the partition plate facing the door in the closed state, wherein the door closes the first chamber; and a burner assembly disposed in the second chamber to supply heated air into the first chamber, wherein the burner assembly comprises: a burner cover (130, 630, 730) to partition the second chamber into a combustion chamber and an exhaust chamber, a burner disposed in the combustion chamber for burning gas to generate flame, a fan disposed in the exhaust chamber, and a nozzle holder disposed outside a rear wall of the cavity, the nozzle holder having a gas spraying hole to spray the gas into the burner, the burner comprises a supply part to receive gas and air, the supply part passing through the rear wall of the cavity, wherein the supply part comprises a plurality of first guides (121, 122) to align the supply part with the gas spraying hole, the plurality of first guides (121, 122) being spaced apart from each other; wherein the nozzle holder comprises a plurality of second guides (224, 225) to guide the plurality of first guides (121, 122) of the supply part, wherein the nozzle holder has an accommodation groove in which the plurality of first guides (121, 122) is accommodated, and the plurality of first guides (121, 122) contacts the plurality of second guides (224, 225) in the state where the plurality of first guides (121, 122) is accommodated into the accommodation groove, wherein the accommodation groove is disposed between the plurality of second guides (224, 225) of the nozzle holder, and wherein the plurality of first guides (121, 122) of the supply part is accommodated into the accommodation groove of the nozzle holder in the state where the plurality of first guides (121, 122) is disposed between the plurality of second guides (224, 225) of the nozzle holder. a burner cover (130, 630, 730) to partition the second chamber into a combustion chamber and an exhaust chamber, a burner disposed in the combustion chamber for burning gas to generate flame, a fan disposed in the exhaust chamber, and a nozzle holder disposed outside a rear wall of the cavity, the nozzle holder having a gas spraying hole to spray the gas into the burner, the burner comprises a supply part to receive gas and air, the supply part passing through the rear wall of the cavity, wherein the supply part comprises a plurality of first guides (121, 122) to align the supply part with the gas spraying hole, the plurality of first guides (121, 122) being spaced apart from each other; wherein the nozzle holder comprises a plurality of second guides (224, 225) to guide the plurality of first guides (121, 122) of the supply part, wherein the nozzle holder has an accommodation groove in which the plurality of first guides (121, 122) is accommodated, and the plurality of first guides (121, 122) contacts the plurality of second guides (224, 225) in the state where the plurality of first guides (121, 122) is accommodated into the accommodation groove, wherein the accommodation groove is disposed between the plurality of second guides (224, 225) of the nozzle holder, and wherein the plurality of first guides (121, 122) of the supply part is accommodated into the accommodation groove of the nozzle holder in the state where the plurality of first guides (121, 122) is disposed between the plurality of second guides (224, 225) of the nozzle holder.