To provide a gas heating method for directly and efficiently heating a gas by using a heater capable of raising its temperature at a high speed without being corroded by the gas, and to provide a compact gas heating device capable of saving the energy.

A zigzag gas channel A is formed by alternately arranging a plurality of flat ceramic heaters 30 or heater units formed by combining the ceramic heaters in a staircase pattern, and the gas supplied to the gas channel A is directly heated by the ceramic heaters 30 or heater units. This gas heating device 10 can be used for heating an exhaust gas or its diluted gas in a processing device for a NOx-containing exhaust gas or a harmful or poisonous exhaust gas.