Provided is an operation state switching device of a pump with variable capacity. When the pump with variable capacity is in half-capacity operating state, the pump with variable capacity is switched to a full-capacity operating state by reliably determining the insufficient exhausted flow in order ensure the speed changing function and lubrication function of a speed changer. When a heat determining unit (M3) determines a lock-up clutch arranged by the speed changer (T) generates heat, the lock-up clutch is slipped because of the insufficient exhausted flow of the pump with variable capacity (OP).As a result, an operation state switching unit (M4) switches the pump with variable capacity from the half-capacity operating state to the full-capacity operating state. Therefore, the exhausted flow of the pump with variable capacity can be increased in order to prevent the durability of the lock-up clutch form declining and guarantee the speed changing function and lubrication function of the speed changer. In addition, from a time point when the lock-up clutch is determined heated and after a preset time, the half-capacity operating state of the pump with variable capacity is permitted. Therefore, the heat generation of the lock-up clutch can be prevented in advance.