A controller of an internal combustion engine capable of spark ignition combustion and compression ignition combustion which restrains the degradation of operation performance and exhaust performance at the time of combustion type switching. The controller includes control means for performing combined combustion which leads to ignition combustion by a pressure rise by spark ignition combustion through adjustment of an internal cylinder temperature and a combustion speed at the end of compression, wherein the combined combustion is performed in the process of combustion type switching between spark ignition combustion and compression ignition combustion based on a result of determination of whether or not combustion type switching is possible, thus implementing a smooth combustion type switching.