A cooking appliance comprising a cavity having a through hole and a lighting device for illuminating an inside of the cavity, the lighting device comprising: a light source comprising a light emitting diode, LED,, the light source is installed outside of the cavity adjacent the through hole that connects an inside and outside of the cavity; a light tube installed outside the cavity and connected to the light source, wherein a first portion of the light tube is provided outside the cavity such that the first portion of the light tube is exposed to the inside of the cavity via the through hole, the light tube being formed in a rod shape having a length extending in the vertical direction, wherein the light emitted from the LED is received via a light incidence surface of the light tube facing the LED and is diffused in an area where the through hole is formed; a supporter installed outside the cavity to support the light source such that the light source is spaced apart from the cavity, a transmissive cover installed in the cavity to cover the through hole and to transmit the light diffused from the light tube into the cavity, characterized by a rear cover installed on an outer side surface of the cavity to cover the through hole and coupled with the transmissive cover via the light tube therebetween, and by the supporter comprising a coupling portion that fixes the supporter outside the cavity, a supporting portion extended in a vertical direction from the coupling portion that supports the light source such that the light source is spaced apart from the coupling portion in the vertical direction, and a fixing portion that fixes the light tube such that the light incidence surface faces the LED, wherein an upper side of the light tube is fixed to the supporter and wherein a lower side of the light tube is inserted into a space between the transmissive cover and the rear cover and is fixed to the rear cover. a light source comprising a light emitting diode, LED,, the light source is installed outside of the cavity adjacent the through hole that connects an inside and outside of the cavity; a light tube installed outside the cavity and connected to the light source, wherein a first portion of the light tube is provided outside the cavity such that the first portion of the light tube is exposed to the inside of the cavity via the through hole, the light tube being formed in a rod shape having a length extending in the vertical direction, wherein the light emitted from the LED is received via a light incidence surface of the light tube facing the LED and is diffused in an area where the through hole is formed; a supporter installed outside the cavity to support the light source such that the light source is spaced apart from the cavity, a transmissive cover installed in the cavity to cover the through hole and to transmit the light diffused from the light tube into the cavity, characterized by a rear cover installed on an outer side surface of the cavity to cover the through hole and coupled with the transmissive cover via the light tube therebetween, and by the supporter comprising a coupling portion that fixes the supporter outside the cavity, a supporting portion extended in a vertical direction from the coupling portion that supports the light source such that the light source is spaced apart from the coupling portion in the vertical direction, and a fixing portion that fixes the light tube such that the light incidence surface faces the LED, wherein an upper side of the light tube is fixed to the supporter and wherein a lower side of the light tube is inserted into a space between the transmissive cover and the rear cover and is fixed to the rear cover.