To provide a cylinder injection type spark ignition internal combustion engine having improved combustion efficiency in a low load operation region during stratified charge combustion while suppressing the occurrence of smoke with the treatment of greatly delayed ignition for heating an exhaust gas purifying catalyst at starting.

The spark ignition internal combustion engine comprises an injector 10 and an ignition plug 12 arranged near the ceiling center of a combustion camber 5, and a piston whose top face portion is formed into a recessed portion and divided with a partition wall shaped sorting protruded portion 14 protruded from a bottom face portion to construct an ignition stratified mixture flow forming cavity 15 which reflects a sprayed fuel flow 11 injected by the injector 10 to form stratified mixture over the ignition plug 12, and a homogeneous mixture forming cavity 16 which changes the sprayed fuel flow 11 distributed by the sorting protruded portion 14 into homogeneous mixture.