A bloodstream detector includes a covering sheet, light emitters, light receivers, an orientation sensor, and a signal output interface. The covering sheet includes a detection surface. The light emitters are on the covering sheet and emit lights outwardly from the detection surface. The light receivers are on the covering sheet and exposed from the detection surface to receive lights coming toward the detection surface. The orientation sensor is on the covering sheet to detect an orientation change of the bloodstream detector. The signal output interface is coupled to the light receivers and the orientation sensor to output detection signals of the light receivers and the orientation sensor.
