The present disclosure provides a light-on detection device and a light-on detection method. The light-on detection device includes a substrate, and a probe block provided with probes and connected to the substrate. The light-on detection device further includes a flattening element configured to apply a force onto a surface of the display panel so as to change the surface of the display panel from a first shape having a first height difference to a second shape having a second height difference less than the first height difference, thereby to enable the probes to perform the light-on detection on the display panel with the second shape.