To recirculate appropriate quantity of exhaust gas by adjusting an exhaust back pressure of exhaust gas emitted from a diesel engine.

The exhaust pressure adjusting device 7A is arranged on a downstream side from an EGR gas branch point in the middle of an exhaust pipe connected to an exhaust manifold of the diesel engine 1. The exhaust pressure adjusting device is provided with an exhaust gas inlet arranged on an upstream side in a center axis direction of a cylindrical case 10, an exhaust gas outlet arranged on a downstream side in a center axis direction of the cylindrical case, a shuttering board 15 arranged on the upstream side in the case 10, and at least one or more adjusting plates 16 having a passing hole 16c detachably arranged on a downstream side of the shuttering board 15 at a predetermined interval.