A cooktop includes a knob assembly controls a heating part. The knob assembly includes: a knob body disposed at a front surface of a control panel and rotating around a rotation shaft extended in a front-rear direction, a light diffusing part disposed at a rear side of the knob body and diffusing light, and a light source part disposed at a rear side of the light diffusing part and including one or more light sources. The light diffusing part includes a light source corresponding part disposed at a position corresponding to one of the light sources, and a thickness of the light diffusing part along a first straight line that passes from a center of the light diffusing part through the light source corresponding part is greater than a thickness of the light diffusing part along a straight line that does not pass through the light source corresponding part.