To prevent moisture condensation on the substrate of an electronic part assembly without complicating a constitution or limiting the arrangement of an electronic part on the substrate.

In the electronic part assembly 10 provided with the substrate 20 to which the electronic parts are assembled, a connector 30 which is assembled to the substrate 20 and constitutes the electric connection of an external device 60 and the electronic parts, an aperture 40a having nearly the same width as that of the substrate 20, and a case 40 which is formed with a guide groove 41 to guide both ends in the widthwise direction of the substrate 20 from the aperture 40a toward the depth and which houses the substrate 20, and a cover 50 which is formed with a connector aperture 50a and which is combined with the case 40 so as to occlude the aperture 40a while making the connector 30 exposed outside the case 40 via the connector aperture 50a, a stationary pin 31 is fixed to the connector 30, the stationary pin 31 is inserted through an assembling hole 20a formed at the substrate 20, the stationary pin 31 is soldered to the substrate 20, and thereby the connector 30 is assembled to the substrate 20.