To provide a diesel engine with a supercharger capable of effectively preventing water from entering an exhaust pipe while avoiding the lowering of an output efficiency.

In a V-type four-cycle engine 1 supercharged with air by a centrifugal blower type mechanical supercharger 16, when a load on the engine 1 is a specified value or higher, the valve timing of one cylinder row 25a is switchable from two-cycle to four-cycle. In two-cycle, the injection of fuel into the cylinder row 25a is stopped.