NOVELTY - A cylindrical honeycomb base material (5) has a honeycomb portion (3) having a partition (1) which becomes a flow path of fluid, and forms several cells (2) extended from one end surface (11) to other end surface (12). A heat-emitting unit (4) is arranged surrounding the outer periphery of the honeycomb portion. A heat generating element (6) is arranged in the heat-emitting unit to generate heat by electricity supply. A catalyst is supported by the partition of the honeycomb portion.    USE - Honeycomb catalyst for exhaust gas purification apparatus (claimed) used in petrol engine and diesel engine mounted in motor vehicle.    ADVANTAGE - The temperature of honeycomb catalyst is maintained at desired temperature even if the temperature of the waste gas discharged from the heat-emitting unit is heated. The generation of crack produced with thermal stress by differential thermal expansion at the time of temperature change can be prevented. The heat can be transmitted efficiently in the boundary of honeycomb portion and heat-emitting unit, without interrupting the transmission of the heat.    DETAILED DESCRIPTION - The material property of honeycomb base material is more than the heat conductivity of 20 W/mk or more and the thermal capacity of 100 J/m3. The partition thickness of outer peripheral portion which surrounds the center portion is 1.05-2.00 times the partition thickness of the center portion. The heat conductivity and thermal capacity of heat-emitting unit is larger than the heat conductivity and thermal capacity of honeycomb portion. An INDEPENDENT CLAIM is included for exhaust gas purification apparatus comprises a cylindrical can having an entrance opening at one edge portion to accommodate honeycomb catalyst (100) and exit opening at other edge portion. A power supply supplies electricity to the honeycomb catalyst which is arranged at entrance opening of can. The honeycomb catalysts are arranged in series so that the cell of one honeycomb catalyst flowed in from entrance opening of can passes the cell of other honeycomb catalyst while the honeycomb catalyst is arranged at exit opening of can. The diameter in cross section orthogonal to the direction where the cell of honeycomb portion is extended is 0.9 times or more of the diameter in cross section orthogonal to direction where the cell of honeycomb catalyst is extended.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the cell of honeycomb catalyst.    Partition (1)    Cell (2)    Honeycomb portion (3)    Heat-emitting unit (4)    Cylindrical honeycomb base material (5)    Heat generating element (6)    End surfaces (11,12)    Honeycomb catalyst (100)