To provide an opening and closing device which can eliminate the torque fluctuations and ensure a secure unlocking, the opening and closing device based on biaxial hinge ensures that, when the second casing is opened from the close position to the initial opened position, and the stopper plate rotates relative to the first hinge shaft up to the initial opened position, the hinge shaft switcher switches from restraints to the rotation of the first hinge shaft to those to the rotation of the second hinge shaft, thus fixes the stopper plate at the initial opened position. The opening torque of the second casing is merely the sum of the torsion torque of the torsion spring and the friction torque of the first free stop tilting mechanism, and not subject to torque fluctuations. Therefore, the second casing can be securely opened.