Power consumption needed to illuminate a subject is reduced and the subject is continuously monitored. Each of a plurality of light sources emits light to the subject. An imaging circuitry obtains a captured image by imaging the subject. A controller performs light emission control to change a light source that emits light from among the plurality of light sources and causes the imaging circuitry to image the subject. A determiner determines whether a detection target that is pre-determined exists in an image area that is a part of the captured image obtained by the imaging circuitry and corresponds to the light source that emits light during imaging for obtaining the captured image.