1. A cardiopulmonary resuscitation monitoring apparatus comprising: a detecting unit configured to obtain a timing of a chest compression period from a detection signal during execution of cardiopulmonary resuscitation; a pulse oximeter configured to detect a change of a blood volume over the chest compression period based on the timing, and configured to obtain an oxygen saturation from the change of the blood volume; an evaluating unit configured to perform evaluation related to the cardiopulmonary resuscitation based on the oxygen saturation; and an outputting unit configured to perform an outputting operation in accordance with a result of the evaluation.