An electrically-heated catalytic converter comprises a catalyst support which produces heat when electric current is applied, a holding mat made of an electrical insulating material, the holding mat being provided so as to cover an outer circumference of the catalyst support, and a case which houses the catalyst support and holds the catalyst support via the holding mat. The catalytic converter treats gas flowing in the case by a catalyst supported on the catalyst support. The holding mat has a water-absorbing property. An insulation layer made of an electrical insulating material is provided between the case and the holding mat.