CONTROLLER OF HYBRID SYSTEM

A controller of a hybrid system including an internal combustion engine and a motor generator connected to each other via a belt includes processing circuitry configured to execute a power generation process that applies a load to the engine by controlling the motor generator to generate power when a first execution condition of an idling stop is satisfied, a slip rate calculation process that calculates a slip rate of the belt based on a rotational speed of the engine and a rotational speed of the motor generator while the power generation process is being executed, a determination process that determines whether or not a second execution condition of the idling stop is satisfied after waiting until a predetermined period elapses, when the slip rate is equal to or more than a threshold, and an idling stop process, when determining that the second execution condition is satisfied.