An object of the present invention is to provide a ceramic heater making it
possible to suppress an outflow of heat to a supporting case and so on to
make the temperature of its ceramic substrate uniform. The ceramic heater
of the present invention is a ceramic heater wherein a heating element is
arranged on a surface of a ceramic substrate or inside the ceramic
substrate, the surface roughness Rmax of the side face of the ceramic
substrate being from 0.1 to 200 .mu.m according to JIS B 0601.
