A hinge device in which breakage of a structuring part caused by an increase in an internal pressure occurring in overloading is prevented. In the hinge device, a second member is adapted to be rotatable relative to a first member. A case (11) is fixed to either the first member or the second member, and a shaft body (12) capable of rotating relative to the case (11) is fixed to the other. A first chamber (14a) and a second chamber (14b) that are formed between the case (11) and the shaft body (12) are filled with viscous fluid. Between the first and second chambers (14a, 14b) is provided an orifice (48) for narrowing a flow path in which the viscous fluid moves from the first chamber (14a) to the second chamber (14b). The orifice (48) enables the viscous fluid to resist rotation of the shaft body (12). A space region (26) is arranged in the shaft body (12), and a valve body (28) is movably placed in the space region (26). When the pressure of the first chamber (14a) reaches a predetermined level, the valve body (28) moves in the space region (26) to increase the volume of the first chamber (14a).