Evaluation method of evaluating a diagnosing function for a variable valve mechanism of an engine valve in which a desired value used for feedback-control of the variable valve mechanism is subjected to a low-pass filter processing so as to produce a state such that a response delay of the variable valve mechanism is generated, and a transient response of the variable valve mechanism is diagnosed in this state. As a result, if it is not determined that a response delay is generated, it is determined that the diagnosing function is abnormal. An evaluation apparatus for carrying out the method is also disclosed.