CONTROL DEVICE

As for a control device for a turbocharger including a turbine, disposed in an exhaust passage of an internal combustion engine, and a compressor, disposed in an intake passage of the internal combustion engine and driven by the turbine, the control device includes a control unit configured to control the turbine such that a boost pressure of the turbocharger in the intake passage becomes equal to or lower than an allowable value, a first calculation unit configured to calculate a decrease amount of a compressor efficiency of the compressor, and a second calculation unit configured to calculate the allowable value based on an intake air amount in the intake passage, in accordance with the decrease amount.