A control method for an internal combustion engine, wherein the internal combustion engine includes a variable compression ratio mechanism (i) that is structured to vary a mechanical compression ratio of the internal combustion engine and (ii) that has a permissible combustion pressure lower in a middle compression ratio region between a maximum compression ratio and a minimum compression ratio than at the maximum compression ratio or at the minimum compression ratio, and wherein the control method comprises: - setting a target compression ratio (tVCR) of the variable compression ratio mechanism lower than a regular value of target compression ratio which is based on engine operation condition under steady state, in response to presence of a request for acceleration; and - restricting a maximum combustion pressure to be lower in the predetermined middle compression ratio region than in a high compression ratio region with respect to the predetermined middle compression ratio region, by restricting an intake pressure, during a process in which the variable compression ratio mechanism varies in compression ratio to reach the target compression ratio (tVCR). wherein the internal combustion engine includes a variable compression ratio mechanism (i) that is structured to vary a mechanical compression ratio of the internal combustion engine and (ii) that has a permissible combustion pressure lower in a middle compression ratio region between a maximum compression ratio and a minimum compression ratio than at the maximum compression ratio or at the minimum compression ratio, and (i) that is structured to vary a mechanical compression ratio of the internal combustion engine and (ii) that has a permissible combustion pressure lower in a middle compression ratio region between a maximum compression ratio and a minimum compression ratio than at the maximum compression ratio or at the minimum compression ratio, and wherein the control method comprises: - setting a target compression ratio (tVCR) of the variable compression ratio mechanism lower than a regular value of target compression ratio which is based on engine operation condition under steady state, in response to presence of a request for acceleration; and - restricting a maximum combustion pressure to be lower in the predetermined middle compression ratio region than in a high compression ratio region with respect to the predetermined middle compression ratio region, by restricting an intake pressure, during a process in which the variable compression ratio mechanism varies in compression ratio to reach the target compression ratio (tVCR). - setting a target compression ratio (tVCR) of the variable compression ratio mechanism lower than a regular value of target compression ratio which is based on engine operation condition under steady state, in response to presence of a request for acceleration; and - restricting a maximum combustion pressure to be lower in the predetermined middle compression ratio region than in a high compression ratio region with respect to the predetermined middle compression ratio region, by restricting an intake pressure, during a process in which the variable compression ratio mechanism varies in compression ratio to reach the target compression ratio (tVCR).