Heater and its production method

[Problem] To make it possible, in a parallel-type heater in which heater patterns are formed in parallel between terminals, to perform a pre-production resistance adjustment easily without detracting from an intended function of the heater and without requiring skills. [Solution] Provided is a heater 30 in which heater patterns 31, 32 are provided in parallel between terminals A, B, wherein each terminal is divided into a divided terminal 37 having electrical conduction only with the heater pattern 31, and a divided terminal 38 having electrical conduction only with the heater pattern 32. After a heater body 36 is fabricated, in a state prior to mounting a feed bolt 50, resistance adjustment is performed with respect to each of a virtual series path 45 formed between the divided terminals 37, 37 and a virtual series path 46 formed between the divided terminals 38, 38, and then the feed bolt is mounted to each terminal, whereby a plurality of virtual series heater patterns are placed in electrical conduction w