Abstract: The heater 72 of the heater portion includes the linear portions 78 and the bend portions 77. A resistance value per unit length of the bend portions 77 at least at a temperature within a temperature range of no less than 700° C. and no more than 900° C. is lower than a resistance value per unit length of the linear portions 78.

Abstract: A heater unit includes a heater 72 having first bend portions 95 (95a to 95d) and second bend portions 96 (96a to 96f). The first bend portions 95 are turns present in a maximum-temperature area (first area 90a) where the maximum temperature is reached during heating among areas 88 where the turns have a narrower pitch and having apexes facing each other in the short-length direction (left-right direction) of a ceramic substrate. The second bend portions 96 are turns present in areas 89 where the turns have a wider pitch and having apexes facing each other in the short-length direction. The distance X1 [mm] between the first bend portions 95 facing each other is larger than the distance X2 [mm] between the second bend portions 96 facing each other.

Abstract: The heater 72 of the heater portion includes the linear portions 78 and the bend portions 77. A resistance value per unit length of the bend portions 77 at least at a temperature within a temperature range of no less than 700° C. and no more than 900° C. is lower than a resistance value per unit length of the linear portions 78.

Abstract: A heater 72 of a heater portion includes linear portions 78 and bend portions 77. A resistance value per unit length of the bend portions 77 at least at a temperature within a temperature range of no less than 700° C. and no more than 900° C. is lower than a resistance value per unit length of the linear portions 78.

Abstract: A heater unit includes a heater 72 having first bend portions 95 (95a to 95d) and second bend portions 96 (96a to 96f). The first bend portions 95 are turns present in a maximum-temperature area (first area 90a) where the maximum temperature is reached during heating among areas 88 where the turns have a narrower pitch and having apexes facing each other in the short-length direction (left-right direction) of a ceramic substrate. The second bend portions 96 are turns present in areas 89 where the turns have a wider pitch and having apexes facing each other in the short-length direction. The distance X1 [mm] between the first bend portions 95 facing each other is larger than the distance X2 [mm] between the second bend portions 96 facing each other.

Abstract: The heater 72 of the heater portion includes the linear portions 78 and the bend portions 77. A resistance value per unit length of the bend portions 77 at least at a temperature within a temperature range of no less than 700° C. and no more than 900° C. is lower than a resistance value per unit length of the linear portions 78.