A knob assembly, comprising: a knob body that is disposed at a front surface of a control panel and that is configured to rotate with respect to a rotation shaft extended in a front-rear direction of the knob assembly, a knob ring that is disposed at a rear side of the knob body and that has an inner diameter greater than an outer diameter of the knob body, and a light source part that is disposed at the rear side of the knob body and that includes one or more light sources configured to irradiate light to the rear side of the knob body, wherein a portion of a rear surface of the knob body includes a first reflective surface configured to reflect light irradiated from the light source part, and wherein a portion of a surface of the knob ring includes a second reflective surface configured to reflect light reflected from the first reflective surface, the portion of the surface of the knob ring facing the knob body, and wherein the knob body further comprises: a knob that defines an exterior of a front surface of the knob assembly and that defines an opening at a rear side defining a first inner space, a knob inner that is inserted into the first inner space and that defines an opening at a rear side defining a second inner space, and an insert that is inserted into the second inner space, and wherein a portion of the knob inner provides a light diffusing part configured to diffuse light irradiated from the light source part. a knob body that is disposed at a front surface of a control panel and that is configured to rotate with respect to a rotation shaft extended in a front-rear direction of the knob assembly, a knob ring that is disposed at a rear side of the knob body and that has an inner diameter greater than an outer diameter of the knob body, and a light source part that is disposed at the rear side of the knob body and that includes one or more light sources configured to irradiate light to the rear side of the knob body, wherein a portion of a rear surface of the knob body includes a first reflective surface configured to reflect light irradiated from the light source part, and wherein a portion of a surface of the knob ring includes a second reflective surface configured to reflect light reflected from the first reflective surface, the portion of the surface of the knob ring facing the knob body, and wherein the knob body further comprises: a knob that defines an exterior of a front surface of the knob assembly and that defines an opening at a rear side defining a first inner space, a knob inner that is inserted into the first inner space and that defines an opening at a rear side defining a second inner space, and an insert that is inserted into the second inner space, and wherein a portion of the knob inner provides a light diffusing part configured to diffuse light irradiated from the light source part. a knob that defines an exterior of a front surface of the knob assembly and that defines an opening at a rear side defining a first inner space, a knob inner that is inserted into the first inner space and that defines an opening at a rear side defining a second inner space, and an insert that is inserted into the second inner space, and wherein a portion of the knob inner provides a light diffusing part configured to diffuse light irradiated from the light source part.