A simplified diagnostic/monitoring instrument for use in primary screening for sleep-disordered breathing (SDB) has been desired. This study was designed to assess the validity of a newly developed piezoelectric sensor as a simple and noninvasive tool for primary screening for sleep-disordered breathing. Forty-three consecutive patients suspected of having sleep-disordered breathing and 10 healthy volunteers were enrolled. Breathing movement was detected with the piezoelectric sensor (180 × 30 × 1 mm), which was placed under a bed sheet under patients, and simultaneous polysomnographic recordings were obtained. We counted the number of apneas of >10 s, irrespective of central or obstructive, that appeared during Cheyne-Stokes-like breathing with a waxing and waning pattern with an amplitude ratio of >10 in the piezoelectric sensor signal. The correlation coefficient between the number of apneas and apnea–hypopnea index (AHI) was 0.74 (P < 0.0001). The sensitivity/specificity of the number of apneas for distinguishing non-SDB patients from mild SDB patients (AHI ≥ 5) were 92.1/60.0% and those for separating moderate to severe (AHI ≥ 15) and severe (AHI ≥ 30) SDB patients from the other patients were 96.9/100% and 93.8/86.5%, respectively. There were no complaints from patients about the use of the piezoelectric sensor. The results indicate that the number of apneas detected by this piezoelectric sensor during Cheyne-Stokes-like breathing is a potential new index for primary screening for SDB at least for cardiac patients. Thus, the piezoelectric-sensor system might be useful for simple, noninvasive and comfortable SDB screening at home, hospitals and health care facilities.