To display a video of high picture quality and high visibility in a bright room.

A projection system includes: a projection device 20 which includes a video display section for taking in a video signal and displaying the video, and converts the video that the video display section displays into video light to perform projection; a screen device 30 for changing a state of a projection face so that a reflection degree of light on a projection face becomes one of a first reflection degree and a second reflection degree; an illuminating device 40 for switching a state of illumination in an appreciation room R₂ where the screen device 30 is installed in accordance with lighting-on and lighting-out; and a controller 10 for controlling the screen device 30 so that the state of the projection face in the screen device 30 is switched in synchronization with a frame frequency of the video signal, controlling the illuminating device 40 so that the illumination becomes a first illumination state in a period in which the reflection degree of the light becomes the first reflection degree, and controlling the video display section so that the video signal is taken in synchronization with switching timing of the state of the projection face.