To perform highly functional projection with an intuitive operation using a portable terminal.A projection system includes: a portable terminal; a projection device; and a cradle. The portable terminal detects a change in posture of the portable terminal itself. The projection device reproduces a video signal, and projects video thus reproduced on a projection surface. The cradle supports the projection device. The cradle changes the posture of the projection device in accordance with a detection result of the portable terminal.