Heater, heating device, fixing device, and image forming apparatus

A heater includes a base, a resistor pattern, and a circuit breaker. The resistor pattern includes a plurality of rows of resistors extending in a longitudinal direction of the base. The plurality of rows of resistors are spaced away from each other in a short-side direction orthogonal to the longitudinal direction of the base, coupled in parallel, and configured to generate heat by energization. The circuit breaker is disposed across the plurality of rows of resistors in the short-side direction and configured to cut off power supply to the resistor pattern when a temperature of any one of the plurality of rows of resistors reaches a high temperature threshold.