Combustion control device and control method for internal combustion engine

In a control device (50A), using an actual compression ratio calculation unit (502), an actual compression ratio epsilon is calculated on the basis of an air supply pressure (Ps), a pre-ignition compression pressure (Pc), and an air supply temperature (Ts). Using a deposit deposition amount estimation unit (504), a deposit deposition state in a combustion chamber (18) is ascertained on the basis of the deviation Deltaepsilon between the actual compression ratio epsilon and a set compression ratio epsilon'. When the deviation Deltaepsilon exceeds a threshold value, an air-to-fuel ratio or ignition timing of operation conditions of an internal combustion engine are corrected on the basis of a correction map (508), and as a result, a worsening of exhaust gas is suppressed.