A control device for an internal-combustion engine, includes: an ejector including an exhaust port coupled to an intake passage upstream of a compressor, an intake port coupled to a recirculation passage recirculating intake air from the intake passage downstream of the compressor to the intake passage upstream of the compressor, and a suction port coupled to a first branch passage; a first pressure acquirer obtaining a first pressure that is a pressure upstream of the compressor in the intake passage; a second pressure acquirer obtaining a second pressure that is a pressure downstream of the compressor in the intake passage; and an ejector negative pressure estimator configured to estimate an ejector negative pressure based on an opening period of the purge valve and the second pressure.