In an electromagnetically driven shutter of the type having a shutter driving rotor arranged to rotate on the optical axis of a photograph-taking lens, the shutter driving rotor is provided with a circular opening and is formed into an approximately rhombic shape consisting of circumferential parts which are concentric with the circular opening and straight parts which extend in the tangential directions of the circumferential parts. A conductor coil is provided along the periphery of the shutter driving rotor. A magnetic field is arranged to act on the straight parts of the coil to rotate the rotor upon supply of electrical energy.