To provide a waterproof electronic unit, which is easily assembled, whose manufacture cost is low, whose deterioration of the detection characteristic of a pressure sensor accompanying the introduction of impurity is eliminated, and which withstands long-term use.

In a waterproof electronic unit, a pressure sensor which is loaded on a printed board and in which a pressure detection art is connected to a pressure introducing pipe is stored in a case, in which a waterproof connector is installed by filling it with mold resin. The case is constituted of a body and a cover body which is engaged with the upper part of the body and to which a pressure introducing pipe is shaped integrally. A dynamic pressure room connected to the pressure introducing pipe is installed on the filling face of molding resin on the inner side of the cover body. The structure of the waterproof electronic unit, where the pressure introducing part of the pressure sensor is exposed, is constituted in the dynamic pressure chamber.