To provide a kiln that can shorten time for firing and can reduce variation in the porosity and flexural strength of fired bodies, as compared with existing kilns using external heating.

A kiln body 11 has a quadrangular muffle 15 of carbon disposed in a firing chamber 13 made of heat insulating material. In the muffle 15, firing tools 18 are arranged to carry and support fired bodies 17. In the firing chamber 13, a first electrode 22 and a second electrode 23 are arranged as vertically holding the muffle 15 in between. The first electrode 22 and second electrode 23 are each connected to an AC power supply 24 via a power controller 25. The power controller 25 comprises a thyristor circuit to on/off-control power supplied to the muffle 15 according to a command signal from a control device 26.