An electronic device includes a photodetector, a notification light emitter, and a determination component. The photodetector detects reflected light of light from a projection device within a detection region, the projection device projecting the light in a projection region on a projection surface. The notification light emitter emits on the projection surface two notification lines of visible wavelength that approach each other towards the photodetector. The determination component determines that the projection region is at least partially located outside the detection region based on a detection result of the photodetector. The determination component further determines that an edge of the projection region that is located closest to the photodetector is substantially parallel to a line segment that connects ends of the two notification lines.