A combustion control apparatus for an engine having a variable valve timing mechanism capable of varying valve timings of an exhaust valve and an intake valve establishes a combustion mode to either of following three modes, a four-cycle compression ignition combustion mode at a low and medium load area, a two-cycle spark ignition combustion mode at a high load area, and a four-cycle spark ignition combustion mode at a high speed area. When the combustion mode is established to the compression ignition combustion mode, the apparatus establishes the valve timings of the exhaust and intake valves so as to form a negative overlap period in which both exhaust and intake valves concurrently close in the neighborhood of the exhaust top dead center (TDC).