Abstract: A diesel engine (1) has: a flow adjuster (10) for throttling exhaust flow; an intake heater (71) for heating intake air; a thermal medium circulator (72) for circulating a thermal medium to warm the diesel engine (1); a cylinder cut-off device (73) for conducting cylinder cut-off; and a fuel injection timing advancing device (74) for advancing timing for supplying fuel to a cylinder, the respective devices being actuated at least from pre-high-idle step to a neighborhood of high-idle condition, so that fuel combustion stabilization of the diesel engine (1) can be rapidly enhanced during a period where less fuel is supplied into the cylinder and fuel combustion time is short, thus greatly reducing discharge of white smoke and possibility of engine bunching.