Abstract: A pacemaker system comprising apnea detecting means for measuring parameters about respiratory including at least two parameters of the number of apneas per unit time and the period of time during which an apnea continues and detecting an apnea state of a sleeping patient on the basis of the measured parameters, characterized in that when the measured values of the detection parameters measured by the apnea detecting means increase over reference values at which the pacing rate is changed to a preset and stored SAS treating pacing rate, the pacing rate is changed and the pacing mode is changed to an SAS treating pacing mode. The apnea syndrome of the sleeping patient is detected and treated coping with the bradycardia and various problems accompanying the apnea syndrome.